Patent Publication Number: US-2023145676-A1

Title: Infrared sensor device

Description:
FIELD 
     The present disclosure relates to an infrared sensor device. 
     BACKGROUND 
     In a conventional infrared sensor device, an entire sensor has been controlled to a predetermined temperature by a Peltier element to improve a measurement accuracy (e.g., see, Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     
         
         [Patent Literature 1] JP 2012-225717 A 
       
    
     SUMMARY 
     Technical Problem 
     However, the Peltier element is a separate member from a sensor chip, and is attached to the sensor chip from outside. Accordingly, the temperature of the sensor chip cannot be precisely controlled, and the measurement accuracy cannot be sufficiently improved. 
     The present disclosure has been made to solve the above-described problem, and aims at obtaining an infrared sensor device capable of sufficiently improving a measurement accuracy. 
     Solution to Problem 
     An infrared sensor device according to the present disclosure includes: an insulating substrate; a sensor chip bonded to the insulating substrate using a bonding material and having a pixel unit that detects an infrared ray; a heat generation mechanism integrated with the sensor chip; and a control unit provided on the insulating substrate and controlling an amount of current to be supplied to the heat generation mechanism. 
     Advantageous Effects of Invention 
     In the present disclosure, the heat generation mechanism is integrated with the sensor chip. When the amount of current to be supplied to the heat generation mechanism is controlled, the temperature of the sensor chip can be precisely controlled. As a result, a measurement accuracy can be sufficiently improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram illustrating an infrared sensor device according to an embodiment 1. 
         FIG.  2    is a diagram illustrating an internal configuration of the infrared sensor device according to the embodiment 1. 
         FIG.  3    is a diagram illustrating a pixel unit. 
         FIG.  4    is a cross-sectional view illustrating a pixel. 
         FIG.  5    is a cross-sectional view illustrating an example of a heat generation mechanism. 
         FIG.  6    is a cross-sectional view illustrating another example of the heat generation mechanism. 
         FIG.  7    is a diagram illustrating a change in temperature of the sensor chip according to the embodiment 1. 
         FIG.  8    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 2. 
         FIG.  9    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 3. 
         FIG.  10    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 4. 
         FIG.  11    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 5. 
         FIG.  12    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 6. 
         FIG.  13    is a circuit diagram illustrating an example of a sensor chip according to the embodiment 6. 
         FIG.  14    is a circuit diagram illustrating another example of the sensor chip according to the embodiment 6. 
         FIG.  15    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 7. 
         FIG.  16    is a diagram illustrating an amount of current or an amount of heat generation of a heat generation mechanism according to the embodiment 7. 
         FIG.  17    is a diagram illustrating a change in temperature of a sensor chip according to the embodiment 7. 
         FIG.  18    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 8. 
         FIG.  19    is a diagram illustrating the pixel unit according to the embodiment 8. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An infrared sensor device according to the embodiments of the present disclosure will be described with reference to the drawings. The same components will be denoted by the same symbols, and the repeated description thereof may be omitted. 
     Embodiment 1 
       FIG.  1    is a diagram illustrating an infrared sensor device according to an embodiment 1. An infrared sensor device  1  is attached to an air conditioner, for example, and detects a temperature inside a room or a location of a person inside the room with infrared rays. The infrared sensor device  1  includes an insulating substrate  2 , a sensor chip  4  bonded to the insulating substrate  2  using a bonding material  3 , and an ASIC  5  formed on the insulating substrate  2 . The ASIC  5  outputs an infrared detection result of the sensor chip  4  to outside. Power is supplied to the sensor chip  4  and the ASIC  5  from a power supply  6 . 
     The insulating substrate  2  is housed in a case  7  of the air conditioner, for example. A main body and the case  7  of the air conditioner are each composed of plastic. The insulating substrate  2  is a glass epoxy substrate, for example. Examples of the bonding material  3  include a die bonding material of a silicon adhesive or an Ag paste. These members each have a large thermal resistance and thermal capacitance. A thermal resistance between the insulating substrate  2  and the case  7  is large. Therefore, even if each of the sensor chip  4  and the ASIC  5  generates heat when the infrared sensor device  1  operates, the heat is not easily radiated. The heat from the ASIC  5  that has been generated earlier when the infrared sensor device is started up is not easily transmitted to the sensor chip  4 . Accordingly, it has conventionally taken time until the temperature of the sensor chip  4  is stabilized so that an output level and a characteristic of the infrared sensor device are stabilized. 
       FIG.  2    is a diagram illustrating an internal configuration of the infrared sensor device according to the embodiment 1. The sensor chip  4  is a solid-state image sensor having a pixel unit  8  that detects infrared rays. A reading circuit  9 , a chip temperature detector  10 , and a heat generation mechanism  11  are integrated with the sensor chip  4 . The reading circuit  9  reads out signals one by one from a plurality of pixels included in the pixel unit  8 . The chip temperature detector  10  detects the temperature of the sensor chip  4 . 
     The ASIC  5  includes A-D converters  12  and  13 , a control unit  14 , and a current source  15 . The A-D converter  12  converts an output signal of the reading circuit  9  into a digital signal. The control unit  14  receives an output signal from the A-D converter  12 , and outputs the output signal to outside as an infrared detection result. 
     The A-D converter  13  converts an output signal of the chip temperature detector  10  into a digital signal. The control unit  14  performs calculation in response to an output signal of the A-D converter  13 . The current source  15  applies to the heat generation mechanism  11  a variable current determined based on a calculation result of the control unit  14 . Thus, the control unit  14  controls an amount of current to be supplied to the heat generation mechanism  11  in response to an output of the chip temperature detector  10 . 
       FIG.  3    is a diagram illustrating a pixel unit. In the pixel unit  8 , a plurality of pixels  16  are arranged in a matrix shape. A bias voltage is applied to the pixels  16  in a column selected by a column selection switch  17 , and a current flows through the pixels  16  in the column. A current value of the pixel  16  selected by a row selection switch  18  is read out. 
       FIG.  4    is a cross-sectional view illustrating a pixel. A concave cavity  20  is formed by etching in a silicon substrate  19 . The pixel  16  is held by support legs  21  and  22  above the cavity  20 . Therefore, the pixel  16  is hollow insulated from the silicon substrate  19 . The pixel  16  includes an insulating film  23  and a PN diode  24  provided in an inner portion of the insulating film  23 . Insulating films  26  are formed on respective trench structures  25 . Signal lines  27  and  28  are formed in the respective insulating films  26 . A P-type layer  24   a  and an N-type layer  24   b  of a PN diode  24  are respectively connected to the signal lines  27  and  28  via thin film metal wirings  29  and  30  in the support legs  21  and  22 . The PN diode  24  is a thermosensor that changes in electrical characteristic depending on a temperature, and converts a temperature change due to incident infrared rays into an electrical signal. The PN diode may be replaced with another thermosensor such as a resistor. 
       FIG.  5    is a cross-sectional view illustrating an example of a heat generation mechanism. A resistor  31  is an N + -type diffusion layer formed by implanting impurities into a surface of the silicon substrate  19 . The resistor  31  provides the heat generation mechanism  11 . The silicon substrate  19  is of a P type and has a relatively high resistance. A P + -type diffusion layer  32  is formed around the resistor  31  to reduce a resistance value of a P-type region around the resistor  31  and stabilize a potential around the resistor  31 . 
     A field oxide film  33  is formed on the P + -type diffusion layer  32 . An insulating film  34  is formed on the resistor  31  and the field oxide film  33 . Metal wirings  35  and  36  are respectively connected to one end and the other end of the resistor  31  by penetrating through the insulating film  34 . The insulating film  37  covers the insulating film  34  and the metal wirings  35  and  36 . 
     An N + -type diffusion layer of the resistor  31  is formed simultaneously with an N + -type diffusion layer in a source-drain region of an N-type MOSFET in the column selection switch  17  or the row selection switch  18 , for example. Therefore, both the diffusion layers are the same in diffusion depth, impurity concentration, impurity type, and the like. However, the resistor  31  may be a diffusion layer formed simultaneously with a P-type layer of a p-type MOSFET or the P-type layer  24   a  or the N-type layer  24   b  in the pixel  16 , for example, depending on a desired resistance value or temperature characteristic. 
       FIG.  6    is a cross-sectional view illustrating another example of the heat generation mechanism. A field oxide film  33  is formed on a silicon substrate  19 . A resistor  38  is formed on the field oxide film  33 . The resistor  38  provides the heat generation mechanism  11 . An insulating film  34  is formed on the resistor  31  and the field oxide film  33 . Metal wirings  35  and  36  are respectively connected to one end and the other end of the resistor  38  by penetrating through the insulating film  34 . An insulating film  37  covers the insulating film  34  and the metal wirings  35  and  36 . The resistor  38  is formed simultaneously with a gate wiring of a MOSFET in a column selection switch  17  or a row selection switch  18 . Therefore, the resistor  38  is composed of polysilicon having the same thickness and impurity concentration as those of the gate wiring. 
       FIG.  7    is a diagram illustrating a change in temperature of the sensor chip according to the embodiment 1. Immediately after power is turned on, the temperature of the pixel unit  8  is lower than a desired stable temperature. Accordingly, the control unit  14  increases an amount of current to be supplied to the heat generation mechanism  11 . This makes it possible to shorten a time period elapsed until the temperature of the pixel unit  8  reaches a stable temperature. When an environmental temperature increases at time Ta, the temperature of the pixel unit  8  also increases. The control unit  14  reduces the amount of current to be supplied to the heat generation mechanism  11 . Therefore, the temperature of the pixel unit  8  returns to the stable temperature. 
     As described above, in the present embodiment, the heat generation mechanism  11  is integrated with the sensor chip  4 . When the amount of current to be supplied to the heat generation mechanism  11  is controlled, the temperature of the sensor chip  4  can be precisely controlled. As a result, a measurement accuracy can be sufficiently improved. 
     The temperature of the sensor chip  4  changes depending on heat generation at the time of a device operation, a change in outside air temperature, a change in how to be exposed to direct sunlight, and the like. When the temperature of the sensor chip  4  changes, a characteristic such as an output level or a sensitivity of the infrared sensor device changes. The control unit  14  supplies a current to the heat generation mechanism  11  when an output of the chip temperature detector  10  is below a reference value, and stops supplying a current to the heat generation mechanism  11  when the output of the chip temperature detector  10  exceeds the reference value. This makes it possible to make the temperature of the sensor chip  4  constant. Therefore, the output level of the infrared sensor device becomes constant, resulting in stabilized image quality and characteristic. This makes it possible to shorten a time period elapsed until an output of the infrared sensor device is stabilized. 
     Although the stable temperature of the sensor chip  4  is 27° C., for example, the stable temperature changes depending on the outside air temperature. Correspondingly, the control unit  14  also changes the reference value of the output of the chip temperature detector  10  used to control the amount of current to be supplied to the heat generation mechanism  11 . 
     Embodiment 2 
       FIG.  8    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 2. In the present embodiment, a plurality of heat generation mechanisms  11  are arranged around a pixel unit  8  in a surface of a sensor chip  4 . An ASIC  5  individually controls an amount of current to be supplied to each of the plurality of heat generation mechanisms  11 . 
     When the infrared sensor device is started up, heat is transmitted from the ASIC  5  so that a temperature in the surface of the sensor chip  4  varies. At the time of the startup, a control unit  14  makes an amount of current to be supplied to the heat generation mechanism  11  arranged far from the ASIC  5  greater than an amount of current to be supplied to the heat generation mechanism  11  arranged close to the ASIC  5 . As a result, the variation in the temperature in the chip surface is alleviated, thereby making it possible to further shorten a time period elapsed until an output of the infrared sensor device is stabilized. 
     Embodiment 3 
       FIG.  9    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 3. In the present embodiment, a plurality of pairs of heat generation mechanisms  11  and chip temperature detectors  10  are arranged around a pixel unit  8  in a surface of a sensor chip  4 . Therefore, a temperature distribution in the chip surface can be detected. The control unit  14  individually controls an amount of current to be supplied to each of the plurality of heat generation mechanisms  11  in response to an output of the corresponding chip temperature detector  10 . As a result, a variation in temperature in the chip surface is alleviated, thereby making it possible to further shorten a time period elapsed until an output of the infrared sensor device is stabilized. 
     Embodiment 4 
       FIG.  10    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 4. When there has been a change in outside air temperature, heat generation of an insulating substrate  2 , or a change in how to be exposed to direct sunlight, for example, the temperature of the insulating substrate  2  changes prior to a sensor chip  4 . In the present embodiment, a substrate temperature detector  39  that detects the temperature of the insulating substrate  2  is provided in the insulating substrate  2 . A control unit  14  controls an amount of current to be supplied to a heat generation mechanism  11  in response to an output of the substrate temperature detector  39 . As a result, even when the outside air temperature or the like has sharply changed, a change in temperature of the sensor chip  4  is predicted so that the amount of current to be supplied to the heat generation mechanism  11  can be controlled. Therefore, it is possible to further shorten a time period elapsed until an output of the infrared sensor device is stabilized. 
     Embodiment 5 
       FIG.  11    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 5. Two terminals, i.e., a terminal that reads out a pixel output and a terminal that reads out temperature information are required in the embodiment 1. In the present embodiment, a reading circuit  9  not only reads out a pixel output of a pixel unit  8  and provides the pixel output to a control unit  14  but also reads out an output of a chip temperature detector  10  and provides the output to the control unit  14 . 
     When the pixel output of the pixel unit  8  and the output of the chip temperature detector  10  are thus read out by the same reading circuit  9 , the pixel output and the temperature information can be read out by the same terminal. The number of A-D converters that each converts an output signal of the reading circuit  9  into a digital signal and provides the digital signal to the control unit  14  can be set to one. Therefore, a configuration of the infrared sensor device is simplified, resulting in reduced power consumption and cost. 
     Embodiment 6 
       FIG.  12    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 6. In the present embodiment, a chip temperature detector  10  is a diode or a resistor that has not been hollow insulated from a silicon substrate  19 , and is arranged in an inner portion or an outer peripheral portion of a pixel unit  8 . Specifically, this structure is identical to the structure illustrated in  FIG.  4    except that there is no cavity  20 . 
       FIG.  13    is a circuit diagram illustrating an example of a sensor chip according to the embodiment 6. The pixel unit  8  has a photosensitive pixel, and has its anode supplied with a voltage VD 1  and has its cathode grounded via a current source  40 . The chip temperature detector  10  is a non-hollow pixel, and has its anode supplied with a voltage VD 2  and has its cathode grounded via a current source  41 . A reference voltage is applied to respective first inputs of differential amplifiers  42  and  43 . A cathode voltage of the pixel unit  8  is input to a second input of the differential amplifier  42 . A cathode voltage of the chip temperature detector  10  is input to a second input of the differential amplifier  43 . A scanning circuit  44  outputs respective output signals of the differential amplifiers  42  and  43  to an ASIC  5  via an output terminal of a sensor chip  4 . 
       FIG.  14    is a circuit diagram illustrating another example of the sensor chip according to the embodiment 6. A reference voltage is applied to a first input of a differential amplifier  45 . A switch  46  selects one of a cathode voltage of the pixel unit  8  and a cathode voltage of the chip temperature detector  10  and provides the selected cathode voltage to a second input of the differential amplifier  45 . An output signal of the differential amplifier  45  is output to the ASIC  5  via the output terminal of the sensor chip  4 . 
     As described in the embodiment 1, the pixel unit  8  in the infrared sensor is a diode or a resistor that has been hollow insulated from the silicon substrate  19 . A diode or a resistor of the chip temperature detector  10  has the same configuration as that of the diode or the resistor of the pixel unit  8  except that it has not been hollow insulated, whereby a part of a manufacturing process can be shared therebetween. The chip temperature detector  10  can be configured by the diode or the resistor thereof not being hollow insulated, thereby making it possible to obtain a measurement result conforming to an actual temperature of the pixel unit  8 . 
     Embodiment 7 
       FIG.  15    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 7.  FIG.  16    is a diagram illustrating an amount of current or an amount of heat generation of a heat generation mechanism according to the embodiment 7. In the present embodiment, a control unit  14  measures a time period elapsed since power was supplied from a power supply  6  using a timer, and increases an amount of current to be supplied to a heat generation mechanism  11  in a predetermined time period, e.g., approximately several seconds to several ten of seconds and reduces the amount of current to be supplied to the heat generation mechanism  11  after the predetermined time period has elapsed. Accordingly, an amount of heat generation of the heat generation mechanism  11  increases for only the predetermined time period after the power is turned on. 
       FIG.  17    is a diagram illustrating a change in temperature of a sensor chip according to the embodiment 7. The temperature of a pixel unit  8  gradually rises after the power is turned on. If there is no heat generation mechanism  11 , a time period T 1  is required until the temperature of the sensor chip  4  is stabilized. When the amount of heat generation of the heat generation mechanism  11  is increased for only the predetermined time period after the power is turned on, as in the present embodiment, a time period required until the temperature of the sensor chip  4  is stabilized can be shortened to a time period T 2 . This can result in shortening a time period elapsed until an output level and a characteristic of the infrared sensor device are stabilized since the infrared sensor device was started up. 
     Although there is provided no chip temperature detector  10  in the present embodiment, a method for controlling an amount of current in the present embodiment may be combined with the respective configurations in the embodiments 1 to 6 each including the chip temperature detector  10 . 
     Embodiment 8 
       FIG.  18    is a diagram illustrating an internal configuration of an infrared sensor device according to an embodiment 8. Although the heat generation mechanism  11  is integrated with the sensor chip  4  in each of the embodiments 1 to 7, a pixel unit  8  also serves as a heat generation mechanism in the present embodiment. 
       FIG.  19    is a diagram illustrating the pixel unit according to the embodiment 8. A control unit  14  switches a column selection switch  17  and a row selection switch  18 , to control a plurality of pixels  16 . The control unit  14  causes a current to flow through only the pixels  16  in a selected column and reads out a current value of the pixel  16  in a selected row, as illustrated in  FIG.  3   , when outputting an infrared detection result. When such a heat image is scanned, the sensor chip  4  normally maintains a thermal equilibrium state. 
     The pixel  16  is a diode or a resistor, and thus generates heat when a current is caused to flow therethrough. The control unit  14  causes a current to flow through all the plurality of pixels  16 , as illustrated in  FIG.  19   , to raise the temperature of the sensor chip  4  when an output of a chip temperature detector  10  is below a reference value. As a result, the temperature of the sensor chip  4  can be made constant. Therefore, an output level of the infrared sensor device becomes constant, resulting in stabilized image quality and characteristic. This makes it possible to shorten a time period elapsed until an output of the infrared sensor device is stabilized. Since a heat generation mechanism  11  need not be installed, resulting in reduced cost. Further, heat can be generated in a two-dimensional array shape, thereby making it easy to adjust the temperature of the entire sensor chip  4 . 
     REFERENCE SIGNS LIST 
       1  infrared sensor device;  2  insulating substrate;  3  bonding material;  4  sensor chip;  8  pixel unit;  9  reading circuit;  10  chip temperature detector;  11  heat generation mechanism;  14  control unit;  16  pixel;  24  PN diode;  31 , 38  resistor;  39  substrate temperature detector