JP2007225398A - Thermal infrared detector and thermal infrared sensor - Google Patents

Abstract

A high-sensitivity thermal infrared sensor is realized by improving the heat insulation characteristics of a sensor pixel using a bipolar transistor.
A bipolar transistor (402) and a constant current source (401) having temperature dependence are arranged in a sensor pixel (102a, 102b). The constant current source is disposed between the collector and the base of the bipolar transistor. The collector of the bipolar transistor 402 and one electrode of the constant current source 401 are held by a common supporting leg, and the emitter wiring of the bipolar transistor is held by another supporting leg. Therefore, the number of support legs of the pixel portion can be reduced to two, and the heat insulation characteristics are improved.
[Selection] Figure 4

Description

  The present invention relates to a thermal infrared detector using a transistor as a component of a temperature sensor that detects a temperature change caused by incident infrared rays, and a configuration of a thermal infrared sensor using the same.

  An infrared ray having a wavelength corresponding to the temperature is emitted from the object having heat. By utilizing the thermal effect that depends on the wavelength of infrared rays, the temperature of the sensor element is raised, and the change in the electrical properties of the sensor element due to the temperature rise is detected. Perform detection. Such sensors are required to be as sensitive and miniaturized as possible.

  A configuration for increasing the sensitivity of the thermal infrared sensor is disclosed in Japanese Patent Application Laid-Open No. 11-218442. The thermal infrared sensor disclosed in Patent Document 1 has an electrical characteristic that changes due to a temperature change caused by infrared irradiation, and a detection unit that detects infrared rays by this characteristic change, and the detection unit is held in a substrate cavity. A unit detector (pixel) is configured by the supporting leg portion. Unit detectors are arranged in a two-dimensional array of rows and columns to form a pixel sensor array. This detector is composed of a bipolar transistor or a MOS transistor (insulated gate field effect transistor). An infrared absorber that generates heat by infrared irradiation and supplies the heat to the transistor is provided above the detection surface of the unit detector.

  The heat insulation characteristic of the detection unit is improved by holding the detection unit including the transistor in the substrate cavity. Further, by arranging the infrared absorber, the infrared absorption area is increased to increase the sensitivity. Further, by forming the transistor of the detection portion in a single crystal silicon layer formed over the insulating film, noise due to crystal imperfection is reduced. In addition, the temperature sensor part is formed using the same material as in the transistor element manufacturing process of other circuits of the infrared sensor by forming the detection part using a material generally used in the semiconductor device manufacturing process. Thus, the manufacturing process is simplified.

  Further, as an infrared sensor, there is a resistance barometer type sensor that detects a temperature by attaching a thermosensitive part whose temperature is increased by infrared irradiation to a thermistor and changing the resistance of the thermistor according to the temperature of the thermosensitive part. Patent Document 1 discloses a configuration in which thermistor constant (B constant) expressing the temperature dependence of the thermistor resistance can be finely adjusted to facilitate replacement of the temperature sensor and increase the output voltage. 2 (Japanese Patent Laid-Open No. 11-287713).

  In the configuration disclosed in Patent Document 2, the thermistor constant is adjusted by considering the bipolar transistor equivalently as a thermistor and finely adjusting the base potential of the bipolar transistor. That is, in the temperature detection bipolar transistor, the base potential and collector potential are set so that the collector-base voltage is biased in the reverse direction and the emitter-base voltage is biased in the forward direction, as in normal use. The A power supply voltage is supplied to the collector of the bipolar transistor via a load resistor. The voltage from the stabilized power supply is resistance-divided using a variable resistance voltage dividing circuit and supplied to the base of the bipolar transistor. The resistance value of the variable resistance voltage dividing circuit is finely adjusted under the condition that the emitter-base voltage of the bipolar transistor is in the forward bias state. Using the fact that the barrier height between the emitter and base of a bipolar transistor corresponds to the thermistor constant when the collector resistance is considered as a thermistor, the emitter-base voltage is adjusted to obtain the desired thermistor constant. Plan.

  A thermal infrared image sensor using a MOS transistor as a temperature detection unit (infrared detection unit) is disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2003-101880). In the configuration shown in Patent Document 3, one temperature detector is configured by a plurality of semiconductor elements connected in series. The plurality of semiconductor elements include one PN junction diode having a high operating voltage and a small leakage current, and a plurality of diode-connected MOS transistors having a low operating voltage and a large leakage current. The infrared (temperature) detectors are arranged in a two-dimensional array to constitute a thermal infrared image sensor. When the infrared detector is not selected, the leakage current is reduced by the PN junction diode. Also, the sensitivity is increased by increasing the temperature dependence of the detector current while suppressing an increase in drive voltage by using a plurality of diode-connected MOS transistors.

In addition, the equation representing the temperature dependence of the current of the transistor element and the diode element is described in Non-Patent Document 1 (SM Sze, “Physics of Semiconductor Devices 2nd Edition”, John Willey &Amp; Sons. Inc. 1981 (pages 318 and 451 to 452 of “Physics of Semiconductor Devices, Second Edition”, 1981) by S. M. G.).
Japanese Patent Laid-Open No. 11-218442 JP-A-11-287713 JP 2003-101880 A "SM Sze," Physics of Semiconductor Devices 2nd Edition ", John Willey & Sons. Inc. 1981 (SM Semiconductor" Physics of Semiconductor Devices ", 2nd Edition), pages 318 and 451 to Page 452

  In the thermal infrared sensor, in order to detect a temperature change with high sensitivity, the temperature detection part (temperature sensor) is held by a support leg in a cavity part (concave part) formed on the substrate surface. By using a heat insulating structure that thermally separates the temperature sensor from the substrate as much as possible, a temperature change due to incident infrared rays is accurately generated in the temperature sensor unit.

  One end of the support leg is connected to the substrate, and the other end is coupled to the temperature sensor. This support leg is also used for arranging and wiring the wiring between the temperature sensor unit and the signal line.

  When the bipolar transistor is used as a temperature detecting element as in the above-mentioned Patent Document 1, the bipolar transistor is a three-terminal element, and basically three wires are used as support legs for wiring to each terminal. The above is required. For this reason, the heat insulation characteristic between a temperature sensor part and a board | substrate worsens, and the problem that the high sensitivity as an infrared sensor and pixel size reduction are difficult arises. This Patent Document 1 shows a configuration in which the number of support legs is reduced to two or one by forming a multilayer metal wiring on the support leg and connecting each wiring to each terminal of the transistor element. . However, in order to realize a multilayer wiring structure, there arises a problem that the number of manufacturing steps increases.

  In the configuration shown in Patent Document 2, a bipolar transistor is used as the temperature sensor, and a high-sensitivity temperature sensor can be realized by the amplification action. However, as shown in FIG. 6 of Patent Document 2, the number of supporting legs for heat insulation is required to be three or more, and the supporting legs are provided like a resistance bolometer or a diode type temperature sensor having two terminals. Compared with a configuration that only requires two, the heat insulation characteristics deteriorate, and similarly, there is a problem that it is difficult to increase the sensitivity and reduce the pixel size as an infrared sensor.

  In this Patent Document 2, when used as an infrared image sensor, a configuration is shown in which a bipolar transistor for current amplification and a MOS transistor for pixel selection are provided in a pixel. The MOS transistor is turned on, the collector of the selected pixel is coupled to the data line (horizontal signal line), and the data line is driven by the bipolar transistor. Accordingly, there is a problem in that two transistors are arranged in one pixel, and the pixel size cannot be reduced.

  In the configuration disclosed in Patent Document 3, a diode-connected MOS transistor is used as a diode-type temperature sensor. However, since a series body of diode elements is simply used, in order to cause a sufficient current change, a large number of diode elements are required, and there is a problem that it is difficult to reduce the pixel size. Further, since this detection current amplification function is not provided, there arises a problem that it is difficult to achieve high sensitivity as an infrared sensor.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thermal infrared detector having a high sensitivity and a small occupation area, and a thermal infrared sensor using the thermal infrared detector as a pixel.

  A thermal infrared detector according to the present invention is a thermal infrared detector that is coupled between a selection signal line and a readout signal line and detects a temperature change caused by incident infrared rays, and is connected to a control electrode and the readout signal line. A transistor element having a first electrode connected to the selection signal line, and a current having a temperature dependence, coupled between the control electrode of the transistor element and the read signal line. A current source is provided.

  A thermal infrared sensor according to the present invention includes a plurality of horizontal drive lines, a plurality of vertical drive lines, and a two-dimensional array of rows and columns so as to correspond to the intersections of the horizontal drive lines and the vertical drive lines. A plurality of pixels arranged in a shape are included. Each pixel is disposed in a recess formed on the substrate and detects a temperature change due to incident infrared rays, first and second support legs for holding the temperature sensor on the recess, and a temperature sensor And an infrared absorption part thermally coupled to the substrate. The temperature sensor includes a bipolar transistor element and a current source connected between a base and a collector of the bipolar transistor element to flow a temperature-dependent current.

  This pixel is further disposed on the first support leg, and is arranged on the first support leg and the second support leg for connecting the collector of the bipolar transistor element and the first electrode of the current source to the corresponding vertical drive line. And a second wiring connecting the emitter of the bipolar transistor to the corresponding horizontal drive line.

  The thermal infrared sensor according to the present invention further includes a signal processing circuit that is coupled to a plurality of horizontal drive lines and supplies a bias voltage for selecting a pixel for each pixel row, and between each vertical drive line and a power source. And a plurality of load resistance elements that cause a voltage change according to a detection current of a selected pixel in a corresponding column on a corresponding vertical drive line.

  According to the thermal infrared detector according to the present invention, the number of support legs is two, and the heat insulation characteristics of the temperature sensor unit can be maintained at the same level as that of a thermal bolometer or a diode-type infrared sensor. In addition, by coupling a temperature-dependent current source to the base of the bipolar transistor, it becomes possible to have a current change amplification function in the temperature sensor unit, and the temperature change coefficient of the temperature sensor can be increased. A thermal infrared detector with high sensitivity and a small occupied area can be realized.

  Further, by arranging the thermal infrared detectors as pixels in a two-dimensional array, a thermal infrared sensor having a high sensitivity and a small occupied area can be realized.

[Embodiment 1]
1 is an external view schematically showing an overall configuration of a thermal infrared sensor according to Embodiment 1 of the present invention. In FIG. 1, a thermal infrared sensor 100 is formed on the surface of a silicon substrate 101 and includes a pixel array 103 including a plurality of pixels 102 arranged in a two-dimensional array of rows and columns, and is arranged corresponding to each pixel row. A plurality of horizontal drive lines (selection signal lines) 104 to which pixels in the corresponding row are connected, and vertical drive lines (readouts) arranged corresponding to the respective pixel columns and connected to the pixels in the corresponding column, respectively. Signal line) 105, a vertical signal processing circuit 106 that sequentially drives the horizontal drive line 104 to a selected state in a predetermined sequence, and a horizontal signal processing circuit that outputs a pixel detection signal read on the vertical drive line 105 to the outside. 107 is included.

  The pixel 102, which will be described in detail later, includes a temperature sensor, detects a temperature change caused by incident infrared rays, and generates an electrical signal corresponding to the detected temperature.

  The vertical signal processing circuit 106 sequentially drives the horizontal drive lines 104 to the selected state, so that one row of pixels connected to one horizontal drive line 104 in the pixel array 103 is selected (energized). Detection electric signals (current signals) from the pixels in the selected row are output to the corresponding vertical drive lines 105.

  The horizontal signal processing circuit 107 includes a sample / hold circuit or a selection switch, converts a detection electric signal (current signal) of a pixel appearing on the vertical drive line 105 into a voltage signal, and outputs the voltage signal to the outside sequentially or in parallel. By arranging the pixels 102 in a plurality of rows and columns in the pixel array 103, the temperature distribution due to infrared rays incident from the non-measurement target substance can be detected in accordance with the detection signal of the pixels 102, such as an infrared image sensor. Can be realized.

  Note that a thermal infrared temperature detector is used as the pixel 102, and FIG. 1 shows an example of a pixel array including pixels arranged in two rows and three columns. However, the number of rows and columns (number of horizontal drive lines and vertical drive lines) of the pixels 102 of the pixel array is set to an appropriate number according to the application application or required resolution of the sensor.

  FIG. 2 is a diagram schematically showing a planar layout of the pixel 102 shown in FIG. In FIG. 2, the infrared absorption structure provided in the pixel 102 is not shown in order to simplify the drawing. The infrared absorption structure is thermally coupled to the temperature sensor unit, absorbs incident infrared rays, generates heat by the absorbed infrared rays, and transmits the heat to the temperature sensor unit. By using this infrared absorption structure, the infrared irradiation area of the pixel is ensured and heat corresponding to the incident infrared ray is generated.

  In FIG. 2, the region of the pixel 102 is defined by a rectangular frame-shaped separation region 160. This isolation region 160 includes an interlayer insulating film connected to the silicon substrate 101 shown in FIG.

  The pixel 102 includes a temperature sensor unit 202 that detects a temperature change caused by incident infrared rays, and support legs 201 a and 201 b that hold the temperature sensor 202. Etching holes are formed between the temperature sensor unit 202 and the support legs 201a and 201b, and between the support legs 201a and 201b and the separation region 160. The temperature sensor unit 202 is held in a floating state (hollow state) by the support legs 201a and 201b on the surface of a recessed region (hollow part) formed in the lower part thereof.

  By making the temperature sensor portion 202 a hollow structure (a structure in which a hollow portion is provided in the lower portion), temperature changes in the temperature sensor portion 202 are prevented from being transmitted to the silicon substrate 101 shown in FIG. The heat insulation characteristic of the temperature sensor unit 202 is improved. The temperature sensor unit 202 is provided with a temperature sensor 204 that detects the temperature.

  The first support leg 201a has an L shape, and one end thereof is connected to the separation region 160, and the other end is connected to the temperature sensor unit 202 (interlayer insulating film is connected). The second support leg 201 b is formed in the shape of a number 7 that is point-symmetric with the first support leg 201 a, one end of which is connected to the separation region 160, and the other end is the first of the temperature sensor unit 202. Are coupled to a region opposite to the region to which the support legs 201a are coupled (interlayer insulating film is connected).

  These support legs 201a and 201b are provided with wirings 151a and 154b, and the temperature sensor 204 included in the temperature sensor unit 202 is coupled to the signal line (horizontal drive line) 104a and the signal line (vertical drive line) 105b, respectively. To do. On this isolation region 160, signal lines 104a and 104b forming the horizontal drive lines shown in FIG. 1 are continuously extended in the row extending direction, and correspond to the vertical drive lines 105 shown in FIG. Similarly, the signal lines 105a and 105b are continuously extended and arranged on the isolation region 160 in the column extending direction. Pixels in adjacent rows and pixels in adjacent columns are connected to the signal lines 104b and 105a, respectively.

  As shown in FIG. 2, only two support legs, first and second support legs 201a and 201b, are provided as support legs for holding the temperature sensor unit 202 in the hollow part. That is, even when the temperature sensor 204 is provided with a three-terminal element, the number is the same as the number of support legs of the resistance bolometer or the diode-type infrared sensor. Thereby, the number of heat propagation paths between the silicon substrate 101 (separation region 160) and the temperature sensor unit 202 can be reduced, and the heat insulation characteristics of the temperature sensor unit 202 can be improved. Accordingly, the sensitivity of the pixel 102 can be increased and the pixel size can be reduced.

  Further, in the planar layout shown in FIG. 2, by making the lengths of the first support leg 201a and the second support leg 201b as long as possible, the thermal conductance is reduced, and the silicon substrate 101 (isolation region 160) and temperature are reduced. The resistance to heat propagation with the sensor unit 202 is increased to improve the heat insulation characteristics.

  In the planar layout shown in FIG. 2, the horizontal signal lines 104a and 104b in FIG. 2 are described as horizontal drive lines, and the vertical signal lines 105a and 105b correspond to vertical drive lines. However, the planar layout shown in FIG. 2 is rotated by 90 °, the wiring 154a on the first support leg 201a is connected to the vertical drive line, and the wiring 154b on the second support leg 201b is coupled to the horizontal drive line. May be.

  FIG. 3 schematically shows a cross-sectional structure taken along line 3A-3A shown in FIG. In FIG. 3, an infrared absorption structure 301 is provided so as to occupy the most area of the pixel 102 and to be separated from each other between adjacent pixels. This infrared absorption structure 301 has an umbrella structure, is held by the temperature sensor unit 202 by a holding unit formed in a low part, and is thermally coupled.

  The separation region 160, the support leg 201a, the temperature sensor unit 202, and the second support leg 201b are separated from each other via the etching hole 162. A recess 203 is formed in the silicon substrate 101 below the support legs 201 a and 201 b and the temperature sensor unit 202. The recess 203 has a hollow structure. Therefore, in the pixel region shown in FIG. 3, the support legs 201 a and 201 b and the temperature sensor unit 202 are held in a floating state in the cavity of the recess 203. As shown in FIG. 2, these support legs 201 a and 201 b are each connected to and held at the separation region 160 at the end, and are connected to the temperature sensor unit 202 to hold the temperature sensor unit 202.

  A wiring 205 is formed in the separation region 160, the support legs 201 a and 201 b, and the temperature sensor unit 202. Wiring 205 in isolation region 160 corresponds to vertical drive lines 105a and 105b, for example, and wiring 205 in support legs 201a and 201b corresponds to signal lines 154a and 154b shown in FIG.

  In the temperature sensor unit 202, a temperature sensor 204 and a wiring 205 are provided. The wiring 205 in the temperature sensor unit 202 is used to interconnect a current source and a bipolar transistor that constitute the temperature sensor 205, and to connect the wiring on the support leg and the inside of the temperature sensor.

  As shown in FIG. 3, by keeping the temperature sensor unit 202 in a hollow state, the temperature sensor unit 202 and the silicon substrate 101 can be thermally separated as much as possible, and the heat insulation characteristics can be improved. . In addition, by providing the infrared absorption structure 301, a temperature change corresponding to the incident infrared ray is caused in the infrared absorption structure 301, and heat formed by the infrared absorption structure 301 is transmitted to the temperature sensor 204 of the temperature sensor unit 202. . By thermally coupling the infrared emergency structure 301 having a large area to the temperature sensor 204, the area of the infrared absorption region of the pixel can be sufficiently increased even when the layout area of the temperature sensor unit 202 is small, A temperature change corresponding to the incident infrared ray can be detected with high sensitivity by the temperature sensor 204.

  FIG. 4 is a diagram showing an electrical circuit configuration of the pixel 102 and the horizontal signal processing circuit 107 shown in FIG. FIG. 4 representatively shows two pixels 102 a and 102 b coupled to one vertical drive line 105. Pixel 102a is coupled between vertical drive line 105 and horizontal drive line 104a, and pixel 102b is coupled between vertical drive line 105 and horizontal drive line 104b. Each of the pixels 102a and 102b is supplied with a constant current source 401 having temperature dependency and a base current from the constant current source 401. When conducting, the pixel 102a and 102b supply current from the vertical drive line 105 to the horizontal drive line 104 (104a or 104b). An npn bipolar transistor 402 is included. The constant current source 401 and the bipolar transistor 402 constitute a temperature sensor 204.

  Bipolar transistor 402 has a collector coupled to vertical drive line 105 and an emitter coupled to a corresponding horizontal drive line 104 (104a or 104b). Constant current source 401 is coupled between the collector and base of bipolar transistor 402.

  The constant current source 401 is formed using, for example, a diode-connected MOS transistor (insulated gate field effect transistor). The current that the constant current source 401 flows differs according to the temperature characteristics of the elements that constitute the constant current source 401. One electrode of the constant current source 401 of one column of pixels and the collector of the bipolar transistor are connected to the vertical drive line 105 in common.

  The horizontal signal processing circuit 107 includes load resistance elements 403 provided corresponding to the respective vertical drive lines 105. The load resistance element 403 has one end coupled to the power supply line 404 and the other end coupled to the corresponding vertical drive line 105. An output OUT is output from a connection portion between the vertical drive line 105 and the load resistance element 403. The load resistance element 403 generates a voltage drop corresponding to the current flowing through the bipolar transistor of the selected pixel, and generates a voltage signal as the output OUT.

  One row of pixels 102 is coupled to the horizontal drive lines 104a and 104b, respectively. Therefore, an electrical signal indicating the detection result by the pixels 102 in one row is generated in each corresponding vertical drive line 105, and the output OUT from the pixels in one row is passed through the sample / hold circuit by the horizontal signal processing circuit 107. Alternatively, the signals are sequentially selected by the selection gate and output to the outside.

  Next, the infrared detection principle of the thermal infrared sensor shown in FIGS. 1 to 4 will be described. The subject to be imaged by the thermal infrared sensor 100 shown in FIG. 1 emits infrared rays having a wavelength corresponding to the temperature by the heat. When infrared rays from the subject are incident on the pixel array 103 shown in FIG. 1, the incident infrared rays are absorbed by the infrared absorption structure 301 shown in FIG. 3, and the temperature rises due to the thermal effect of the infrared rays. The infrared absorption structure 301 and the temperature sensor unit 202 are thermally coupled, and the temperature of the temperature sensor unit 202 also rises accordingly. The electrical characteristics of the constant current source 401 change according to the temperature of the temperature sensor unit, and the current flowing through the constant current source 401 changes accordingly.

  The bipolar transistor 402 amplifies the temperature change of the current flowing through the constant current 401. For the selected pixel (pixel 102b in FIG. 4), the corresponding horizontal drive line 104b is set to L level, while in the non-selected pixel 102a, the corresponding horizontal drive line 104a is at the power supply voltage level. Set to H level. The base-emitter junction of the bipolar transistor 402 functions as an energization (conduction; on / off state) control switch of the pixel 102. That is, when energizing a pixel with the pixel selected, the potential of the corresponding horizontal drive line (104) is set to the ground voltage level L level, and the horizontal drive line for the non-selected row is maintained at the power supply voltage level H level. To do. As a result, the base-emitter junction of the bipolar transistor of the selected pixel is forward-biased, and the bipolar transistor 402 operates in the saturation region. On the other hand, the base-emitter junction of the bipolar transistor of the non-selected pixel is biased in the reverse direction, and the bipolar transistor 402 is a cut-off region, and the current flow path is cut off. Accordingly, in the non-selected pixel 102a, the bipolar transistor 402 is maintained in the cut-off state, and no current flows from the vertical drive line 105 to the corresponding horizontal drive line 104a.

  On the other hand, in the pixel 102b in the selected state, the corresponding horizontal drive line 104b is at the L level (for example, the ground voltage level), and the bipolar transistor 402 becomes conductive. Therefore, the temperature change of the base current supplied from the constant current source 401 is amplified by the conductive bipolar transistor 402, and the current flowing from the vertical drive line 105 to the corresponding horizontal drive line 104b also changes.

  A load resistance element 403 is coupled to the vertical drive line 105. Therefore, a voltage change corresponding to the current flowing through the pixel 102b in the selected state is generated at the output OUT. By this load resistance element 403, the current driven by the bipolar transistor 402 is converted into a voltage signal to generate an output voltage OUT, and incident infrared rays are detected.

  These horizontal drive lines 104a and 104b are driven by the vertical signal processing circuit 106 shown in FIG. The vertical signal processing circuit 106 is formed of, for example, a shift register, and sequentially drives the horizontal drive lines to the L level selected state in accordance with, for example, the horizontal drive clock signal. By selecting the output voltage OUT generated in each vertical drive line in a predetermined sequence in the horizontal signal processing circuit 107, a voltage signal string having a magnitude corresponding to the temperature of each pixel can be generated.

  As shown in FIG. 4, in the temperature sensor 204, the detection sensitivity can be increased by amplifying by the bipolar transistor 402 using the supply current of the constant current source 401 as the base current. In addition, the silicon substrate 101 and the temperature sensor unit 202 are thermally insulated by the support legs 201 (201a, 201b). Therefore, the smaller the thermal conductance of the support legs 201 (201a, 201b), the more the heat propagation from the temperature sensor unit 202 to the silicon substrate 101 can be reduced, and accordingly the temperature change in the temperature sensor unit 202 is increased. Can do. Thereby, the temperature sensitivity of the temperature sensor unit 202 can be increased, and the pixel size can be reduced.

  Next, in the circuit configuration shown in FIG. 4, the temperature change coefficient of the output voltage OUT is specifically calculated. Now, for the calculation, the circuit shown in FIG. 4 is expressed by the circuit shown in FIG. In FIG. 5, the pixel is in a selected state, and the horizontal drive line to which the emitter of bipolar transistor 402 is connected is maintained at the ground voltage level. The collector of bipolar transistor 402 and one electrode of constant current source 401 are coupled to load resistance element 403 through vertical drive line 105.

  The load resistance element 403 has a resistance value Rl and allows a current Ic to flow. The constant current source 401 is composed of a diode-connected N-channel MOS transistor 415 whose gate and drain are connected to a vertical drive line, and supplies a saturation current Io in the forward direction from the collector of the bipolar transistor 402 to the base. A base current Ib is supplied from the constant current source 401 to the bipolar transistor 402. The bipolar transistor 402 has a grounded emitter current gain hfe, and flows a current of hfe · Ib as a collector current to discharge the emitter current Ie. The output voltage Vout is output from the collector of the bipolar transistor 402 as a detection result output (OUT) by the load resistance element 403. Note that a power supply voltage Vdd is applied to the power supply line 404.

  When the notation shown in FIG. 5 is used, the following equation is established.

  When these equations (1) to (3) are solved for the output voltage Vout, the following equation (4) is obtained, and when the output voltage Vout is differentiated by the temperature T, equation (5) is further obtained.

  Here, the temperature dependence of the resistance value Rl of the load resistance element 403 and the grounded emitter current amplification gain hfe of the bipolar transistor 402 is sufficiently smaller than the temperature dependence of the current Io flowing through the constant current source 401 and can be ignored. I think I can.

  The constant current source 401 is composed of a diode-connected MOS transistor in the first embodiment, and the current Io supplied from the constant current source 401 is the saturation current of the MOS transistor, and is expressed by the following equation (6). .

  Here, β and Vth represent the gain coefficient and threshold voltage of MOS transistor 415, respectively. The gain coefficient β and the threshold voltage Vth have temperature dependence. Therefore, when the equation (6) is differentiated by the temperature T, the following equation (7) is obtained.

  Here, according to pages 451 to 452 of “Physics of Semiconductor Devices, Second Edition” by Sze of the aforementioned Non-Patent Document 1, the gain coefficient β and the threshold voltage Vth of the MOS transistor The typical temperature dependence is expressed by the following equations (8) and (9). Therefore, using these equations (8) and (9), the above equation (7) can be transformed into the following equation (10).

  In Equation (9), the temperature change of the threshold voltage Vth indicates a change millivolt (mV) per Kelvin temperature K.

  For example, if T = 300K, Vth = −0.05V, Rl = 250 kΩ, Io = 1 μA, and hfe = 10 as easy-to-implement values, the temperature change of the current Io supplied from the constant current source 401 can be expressed by the following equation (11 When the equation (11) is substituted into the equation (5), the temperature change coefficient of the output voltage Vout represented by the following equation (12) is obtained.

  That is, as shown in Expression (12), the amount of change voltage per Kelvin temperature K of the output voltage Vout is −200 millivolts (mV). As a typical other type of sensor, a resistance bolometer type sensor has a resistance temperature change coefficient of about 2% / K and a bias voltage of about 3V. Therefore, the temperature change coefficient of the output voltage is about 60 mV / K. Further, in the diode type sensor using the temperature dependence of the forward voltage of the diode, the temperature change coefficient of the output voltage is about 10 mV / K in the configuration where eight diodes are connected in series. Therefore, as shown in the above equation (12), it can be seen that the temperature sensor according to the first embodiment has a temperature change coefficient that is three times or more larger than that of the conventional temperature sensor.

  Further, in the configuration of the infrared detector (pixel) according to the first embodiment, the number of the heat-insulating support legs may be the same as that of the resistance bolometer or the diode type sensor. Therefore, it is possible to realize a thermal infrared sensor in which the heat insulating property of the support leg is good and the high temperature change coefficient, which is an advantage of the transistor method, can be used sufficiently effectively.

  Next, a desirable value of the current Io flowing through the constant current source 401 and the resistance value Rl of the load resistance element 403 will be described.

  The output voltage Vout is a value obtained by subtracting the voltage drop in the load resistance element 403 from the power supply voltage Vdd. Therefore, in order to maximize the output amplitude, it is desirable that the output voltage Vout is about ½ times the power supply voltage Vdd. The power supply voltage Vdd is generally on the order of several volts, for example, 5V. In this case, a desirable value of the output voltage Vout is 2.5V, and the following expression (13) is established.

  Therefore, Io · Rl˜0.25. Therefore, in the first embodiment, Rl = 250 kΩ and Io = 1 μA are set.

  6 (A) to 6 (B) are cross-sectional views showing a manufacturing process of the thermal infrared sensor according to the first embodiment of the present invention. FIG. 6 shows a cross-sectional structure of a portion corresponding to one pixel 102.

  First, as shown in FIG. 6A, a silicon oxide film layer 601 and a silicon single crystal layer 602 are sequentially deposited on a silicon substrate 101 as a pixel formation substrate 600, which is a so-called SOI (silicon on-state). -Insulator) Prepare the board. This silicon substrate 101 functions as a support substrate for the infrared sensor.

  Next, as shown in FIG. 6B, an isolation oxide film 603 is formed at a predetermined position by using a well-known selective oxidation isolation method or trench isolation method. The formation of the isolation oxide film 603 defines a region of the single crystal silicon layer 602 that forms a transistor constituting a temperature sensor of a peripheral circuit such as a pixel and a signal processing circuit.

  Next, as shown in FIG. 6C, the signal processing circuits 106 and 107 (not shown in FIG. 6C) and the pixel array 103 (see FIG. 1) shown in FIG. A diode, a transistor, and the like are formed in the single crystal silicon layer 602 in a region to be formed by using a well-known photolithography, etching method, and ion implantation method. Thus, the temperature sensor 204 is formed in the single crystal silicon layer 602 corresponding to the pixel region.

Next, as shown in FIG. 6D, an insulating film 604 is deposited on the entire surface of the infrared sensor.
Next, as shown in FIG. 6E, after a wiring layer is formed on the insulating film 604, the wiring layer is patterned using a photoengraving and etching method to form a wiring having a predetermined shape (pattern). 205 is formed. Here, in FIG. 6E, the wiring 205 is shown to be embedded in the insulating film 604. However, after a wiring material is deposited on the entire surface of the insulating film 604 and patterned, the insulating film is again deposited on the wiring 205 as a protective film. As a result, a protective film and a temperature sensor support leg against etching at the time of forming the recess are formed (the insulating film around the temperature sensor 204 is continuously formed with the insulating film for the wiring in other regions).

  Next, as shown in FIG. 6F, an etching hole 162 is opened at a predetermined position of the insulating film 604 to form support legs 201 (201a, 201b). The opening (etching hole) 162 separates the insulating film that covers the temperature sensor portion 202 and the insulating film that forms the support legs 201 (201a and 201b) in the cross-sectional portion shown in FIG. The leg ends are connected to the separation region and the temperature sensor, respectively).

  Next, as shown in FIG. 6F, a sacrificial layer 605 made of, for example, silicon is deposited. The sacrificial layer 605 is formed so as to fill the etching holes 162 provided for forming the support legs and to cover the sensor unit 202 and the support legs 201.

  Next, an etching hole is provided in a predetermined region above the temperature sensor portion of the sacrificial layer 605, and then an infrared absorption structure 301 is formed. The infrared absorption structure 301 may be any material that generates heat by infrared absorption, and a material such as a metal such as aluminum, a silicon insulating film, or a metal silicide can be used.

  Next, as shown in FIG. 6G, an etchant such as xenon fluoride is introduced to remove the sacrificial layer 605, and a hollow recess 203 is formed inside the silicon substrate 101. In this etching, after the sacrificial layer 605 is etched, an etchant is supplied to the silicon substrate 101 through the etching hole 162 shown in FIG. 6F, and the silicon substrate 101 is etched. The infrared absorption structure 301, the temperature sensor of the temperature sensor unit 202, and the wiring 205 are protected by an insulating film, and are protected from the etchant used for forming the hollow structure.

  Through a series of these steps, a pixel (thermal infrared detector) 102 that is supported by support legs 201a and 201b made of an insulating film and constitutes a thermal infrared sensor in which the temperature sensor unit 202 and the infrared absorption structure 301 float in the air. Is completed.

  When forming the bipolar transistor of the temperature sensor 204 of the temperature sensor unit 202, a lateral bipolar transistor structure in which emitter and collector layers are formed on both sides of the base region in the single crystal silicon layer may be used. The constant current source MOS transistor has the same configuration as a well-known SOI structure MOS transistor, and the source and drain regions are formed by ion implantation using a single crystal silicon layer as a substrate region (channel formation region). That's fine.

  As the temperature sensor 204 of the temperature sensor unit 202, it is possible to form a current source and a transistor in a polysilicon or amorphous silicon layer formed by CVD (chemical vapor deposition) on the insulating film (601). It is. However, when these materials are used, there is a problem that noise due to crystal grain boundaries and / or band gap levels is large, and variation in characteristics between pixels is large. As shown in FIG. 6C, noise caused by crystal defects can be reduced by forming a current source and a transistor in a single crystal silicon layer formed over an insulating film. Can be reduced, and variations in characteristics between pixels can be reduced. That is, by forming a bipolar transistor and a current source in the SOI layer 600, it is possible to increase the S / N (signal / noise) ratio and to provide a thermal infrared sensor with small characteristic variation between pixels. Can do. In addition, the transistor of the signal processing circuit of the peripheral circuit is also formed in this single crystal silicon layer and can be operated stably.

  As described above, according to the first embodiment of the present invention, a thermal infrared detector (pixel) is realized by a bipolar transistor in which a current source having temperature dependence is connected between a collector and a base. The heat insulation characteristic of the support leg holding the temperature sensor unit can be made comparable to that of the resistance bolometer and the diode type sensor. In addition, the signal amplification function of this bipolar transistor allows the temperature change coefficient of the current / voltage of the temperature sensor to be larger than that of a resistance bolometer and a diode type sensor, and a highly sensitive thermal infrared sensor and infrared detector are provided. Can be realized.

[Embodiment 2]
FIG. 7 is a diagram showing an electrical circuit configuration in a selected state of the pixel (thermal infrared detector) 102 according to the second embodiment. The overall appearance of the thermal infrared sensor according to the second embodiment of the present invention is the same as that of the first embodiment. The pixel 102 shown in FIG. 7 is different from the pixel 102 shown in FIG. 5 used in Embodiment 1 in the following points. In other words, a PN junction diode 420 that supplies a reverse saturation current is connected between the collector and the base of the bipolar transistor 402 as a current source 401 having temperature dependency. The other configuration of the pixel 102 shown in FIG. 7 is the same as that of the pixel 102 shown in FIG. 5, and corresponding portions are denoted by the same reference numerals, and detailed description thereof is omitted.

  Further, the manufacturing method of the thermal infrared sensor using the thermal infrared detector shown in the second embodiment of the present invention as the pixel is the same as that in the first embodiment. The only difference is that a PN junction diode connected in the reverse direction is formed between the collector and base of the bipolar transistor in place of the diode-connected MOS transistor in the temperature sensor section.

  Also in the second embodiment of the present invention, the infrared detection principle of the thermal infrared sensor is the same as that in the first embodiment. In the following, the temperature change coefficient of the output voltage Vout shown in FIG. 7 is specifically calculated. As the constant current source 401, a PN junction diode 420 connected in the reverse direction is used. Therefore, the relationship represented by the equations (1) to (5) shown in the first embodiment can be used as it is.

  The reverse saturation current Io of the PN junction diode 420 of the constant current source 401 is expressed by the following equation.

  Here, A is a constant, S is the junction area, and Eg is the band gap energy (1.12 eV) of silicon. k is the Boltzmann constant and T is the absolute temperature.

  Since the reverse saturation current Io is used as the supply current of the constant current source 401, the current value is smaller than that in the first embodiment. Therefore, the grounded emitter current gain hfe of the bipolar transistor 402 is set to a large value. Here, suppose that Io = 50 mA and hfe = 100. hfe = 100 can be easily realized by using a normal silicon LSI (Large Scale Integrated Circuit) process.

  When the median value of the output voltage Vout is set to 2.5 V, the resistance value Rl of the load resistance element 403 is obtained as about 500 kΩ from the above equation (13). By using these values, the following formula can be obtained by substituting each value after differentiating both sides with the temperature T from the above formula (14).

  Similar to the comparison object used in the first embodiment, a sensor using a vanadium oxide bolometer as a typical other type of sensor has a resistance temperature change coefficient of about 2% / K and a bias voltage of about 3V. The temperature change coefficient of the output voltage is about 60 mV / K. In the sensor using the temperature dependence of the forward voltage of the diode, the temperature change coefficient of the output voltage is about 10 mV / K in the configuration where eight diodes are connected in series. Therefore, it can be seen that the temperature sensor according to the second embodiment has a temperature change coefficient of 6 times or more than the conventional one.

  Therefore, in the temperature sensor according to the second embodiment, as in the first embodiment, the support legs for the base of the bipolar transistor are not necessary, and the number of the support legs for heat insulation is the same as that of the resistance bolometer and the diode type temperature sensor. Two is enough. Therefore, it is possible to realize a thermal infrared sensor in which the heat insulating property of the support leg is good and the high temperature change coefficient, which is an advantage of the transistor method, is more effectively used.

  In the configuration shown in FIG. 7, the reverse saturation current of the PN junction diode is used as the current Io supplied from the constant current source 401. However, the same effect can be obtained even when a reverse saturation current of a Schottky diode is used as the current supplied from the constant current source 401. In addition, as the diode manufacturing process, the same manufacturing process as that of the bipolar transistor can be used, and an increase in the number of manufacturing processes can be suppressed.

  Further, in the thermal infrared sensor using the pixel according to the second embodiment of the present invention, the same effect as in the first embodiment can be obtained by forming the temperature sensor in the SOI layer as in the first embodiment. it can.

  As described above, according to the second embodiment of the present invention, in the pixel (thermal infrared detector), the reverse saturation current of the diode is amplified by the bipolar transistor, and the number of support legs can be reduced. Further, the amplification function of the bipolar transistor can be used, and a thermal infrared detector and thermal infrared sensor with high sensitivity and a small layout area can be realized without increasing the number of manufacturing steps.

[Embodiment 3]
FIG. 8 shows an electrical circuit configuration of pixel 102 in a selected state of the thermal infrared sensor according to the third embodiment of the present invention. The overall appearance of the thermal infrared sensor according to the third embodiment of the present invention is the same as that shown in FIG. 1 in the first embodiment. In FIG. 8, as in the configuration shown in FIG. 5, the connection between the selected pixel 102 and the corresponding load resistance element 403 is shown together with the current flowing through the pixel at the time of selection.

  The pixel 102 shown in FIG. 8 is different in configuration from the pixel 102 shown in FIG. 7 in the following points. That is, two npn bipolar transistors 402 a and 402 b connected in Darlington connection are used as the bipolar transistor 402. A constant current source 401 is connected between the collector bases of the bipolar 402a. As an example of the constant current source 401, a PN junction diode 420 that supplies a reverse saturation current is shown in FIG. However, as in the first embodiment, a MOS transistor diode-connected in the forward direction may be used.

  Even if bipolar transistors 402a and 402b connected to Darlington are used, only the emitter wiring and the collector wiring are required as signal wirings for the transistors, and the number of support legs is the same as in the first and second embodiments so far. Two. As a manufacturing process of the infrared sensor, a process similar to the process shown in FIGS. 6A to 6G is used. Two bipolar transistors connected in Darlington instead of a single bipolar transistor are formed in the single crystal silicon layer region of the pixel. In addition, a PN junction diode that supplies a reverse saturation current is formed as a constant current source. The other configuration of the pixel shown in FIG. 8 is the same as the configuration of the pixel shown in FIG. 7, and corresponding portions are denoted by the same reference numerals, and detailed description thereof is omitted.

  The reverse saturation current of the PN junction is proportional to the junction area. Therefore, when the pixel area is small, the reverse saturation current may be as small as pA (picoampere). The configuration according to the third embodiment of the present invention is an effective configuration in such a case. By amplifying the reverse saturation current of the PN junction with bipolar transistors 402a and 402b connected in two stages of Darlington, Increase the sensitivity of the sensor.

  Specifically, the temperature change coefficient of the output voltage Vout of the pixel 102 shown in FIG. 8 is calculated. Now, the grounded emitter current gains of bipolar transistors 402a and 402b are hfe1 and hfe2, respectively, and the respective base currents are Ib1 and Ib2. Further, it is assumed that the current supplied from the constant current source 401 is Io, the load resistance element 403 has a resistance value Rl, and the current Ic flows. In this case, the relationship expressed by the following equation (18) is established.

Vout = Vdd−Ic · Rl (18)
The current Ic flowing through the load resistance element 403, the current Io flowing through the constant current source 401, the emitter current Ie1 supplied by the bipolar transistor 402a, and the base current Ib2 of the bipolar transistor 402b are expressed by the following equations (19), (20), And the current Ic flowing through the load resistance element 403 is expressed by the following formula (22) from these formulas (19) to (21).

  The temperature dependence of the reverse saturation current Io of the diode 420 is expressed by the equation (14), as in the case of the second embodiment. Consider a case where the reverse saturation current Io of the diode 420 is further smaller than the value used in the second embodiment and is 500 pA. The grounded emitter current gains hfe1 and hfe2 are 100, the power supply voltage Vdd is 5V, and the desired value of the output voltage Vout is 2.5V. When these values are used, the resistance value Rl of the load resistive element 403 is about 500 kΩ from the above-described equation (13), as in the second embodiment. When the temperature change coefficient of the reverse saturation current Io is obtained using the above-described equation (15), the value is represented by the following equation (25). When Expression (25) is substituted into Expression (24), the temperature coefficient of the output voltage Vout becomes a value represented by the following Expression (26).

  As shown in Expression (26), also in the third embodiment, the same temperature change rate of the output voltage Vout as the temperature change rate shown in the second embodiment is obtained. Therefore, as in the second embodiment, it is possible to generate an output voltage having a temperature change coefficient that is six times greater than that of a sensor using a vanadium oxide bolometer and a sensor using the forward voltage temperature dependency of a diode. it can.

  In the third embodiment, out of the bipolar transistors 402a and 402b connected in Darlington, the current Io supplied from the constant current source 401 is amplified by the bipolar transistor 402a. Therefore, even when the reverse saturation current of the PN junction diode 420 is small, the output voltage Vout described in the first and second embodiments is appropriately set (power supply voltage) without increasing the resistance value Rl of the load resistance element 403. The voltage level of 1/2 of Vdd is set to the median value).

  The appearance and configuration of the pixel or the thermal infrared detector are the same as those in the first and second embodiments, and the same effects as those in the first and second embodiments can be obtained. Similarly to Embodiments 1 and 2, by forming a diode and a transistor of the temperature sensor in the SOI layer, it is possible to realize a pixel and an infrared detector with high sensitivity and small characteristic variation.

  In this constant current source 401, a Schottky diode connected in the reverse direction may be used instead of the PN junction diode 420.

[Embodiment 4]
FIG. 9 shows an electrical equivalent circuit of pixel 102 in the selected state according to the fourth embodiment of the present invention. In the fourth embodiment, the overall appearance configuration of the thermal infrared sensor is the same as the configuration shown in the first embodiment with reference to FIG. In pixel 102 according to the fourth embodiment of the present invention, diode-connected junction field effect transistor (JFET) 430 is used as constant current source 401. In the junction field effect transistor, a PN junction JFET in which the gate and the channel region are maintained in a reverse bias state by a PN junction is used. The saturation current of the junction field effect transistor (JFET) is used as the temperature dependent current Io.

  The other configuration of the pixel 102 shown in FIG. 9 is the same as the configuration of the electrical circuit of the pixel at the time of selection in the first embodiment shown in FIG. 5, and corresponding portions are denoted by the same reference numerals, and Detailed description is omitted.

  Also in the fourth embodiment, the infrared detection principle of the thermal infrared sensor is the same as that in the first embodiment. Hereinafter, specifically, the temperature change coefficient of the output voltage Vout of the pixel 102 according to the fourth embodiment is calculated. The same expression is established in the pixel 102 shown in FIG. 9 from the expression (1) to the expression (5) shown in the first embodiment.

  The saturation current of the diode-connected junction field effect transistor is represented by the following equation according to page 318 of Non-Patent Document 1 described above.

  Here, Z and L indicate a gate width and a gate length, respectively. μ is the carrier mobility, q is the elementary charge, N is the impurity concentration, a is a value of ½ of the channel thickness, and εs is the dielectric constant of silicon. Vbi is the built-in voltage of the PN junction, and ni is the true carrier density.

  When both sides of the above equation (27) are differentiated by the temperature T, the following equation (31) is obtained.

For example, assuming that the impurity concentration N is 10 ¹⁶ / cm ³ , the channel width and the channel length (gate width and gate length) Z and L are 6 μm and 2 μm, respectively, and a is 0.2 μm. The following values are obtained:

Vp = 0.31V, Ip = 15 μA, Vbi = 0.35V,
Io = 0.21 μA to Ib
As in the second and first embodiments, assuming that the grounded emitter current gain hfe is 100 and the voltage drop across the load resistance element 403 is 2.5 V, the resistance value Rl of the load resistance element 403 is about 120 kΩ. The temperature dependence coefficient dVbi / dT of the built-in voltage is equal to the temperature dependence of the PN junction forward voltage drop, and is about 1.8 mV / K. When these values are used, the following equation (32) is obtained.

  As described above, as a typical other type of sensor, a vanadium oxide bolometer type sensor has a resistance temperature change coefficient of about 2% / K, and a bias voltage of 3 V has a temperature change coefficient of about 60 mV / K. . Further, in the sensor using the temperature dependence of the forward voltage drop of the diode, the temperature change coefficient is about 10 m / K in the eight-series connection configuration. Therefore, it can be seen that the temperature sensor according to Embodiment 4 of the present invention has a temperature change coefficient that is three times or more larger than that of the resistance bolometer type sensor.

  Also in the temperature detector or pixel according to the fourth embodiment of the present invention, the number of supporting legs for heat insulation of the pixel is two, that is, the supporting leg for the collector wiring and the supporting leg for the emitter wiring, like the resistance bolometer and the diode type sensor. It is. Therefore, as in the first to third embodiments, it is possible to realize a thermal infrared sensor in which the heat insulating characteristics of the support legs are good and the high temperature change coefficient which is an advantage of the transistor method is more effectively functioned. .

  The manufacturing process of the pixel (thermal infrared temperature detector) according to the fourth embodiment of the present invention is formed using the same process as the manufacturing process shown in FIGS. 6 (A) to 6 (G). At the time of forming the constant current source 401, a PN junction type JFET is formed. Therefore, also in this case, by forming the temperature sensor in the SOI layer, it is possible to realize a thermal infrared sensor that can reduce noise and can reduce variation in characteristics between pixels. .

  In the above description, a JFET whose gate portion forms a PN junction is used as the diode-connected JFET in the constant current source 401. However, the same effect can be obtained even when a JFET using a Schottky barrier generally used as a MESFET (metal-semiconductor FET) for gate isolation is diode-connected and its saturation current is used.

  When the current Io flowing through the constant current source 401 is small, a Darlington-connected bipolar transistor may be used for current amplification as shown in the third embodiment.

[Embodiment 5]
FIG. 10 shows a structure of a main part of the thermal infrared sensor according to the fifth embodiment of the present invention. The overall appearance of the thermal infrared sensor according to Embodiment 5 of the present invention is the same as that shown in FIG. In the thermal infrared sensor according to the fifth embodiment of the present invention, the following points are different from the configurations shown in the first to fourth embodiments. That is, in the horizontal signal processing circuit 107, one end of the load resistance element 403 is coupled to the ground line 704 that supplies the ground voltage Vss. In the pixels 102a and 102b, a PNP bipolar transistor 702 is provided as a bipolar transistor. A constant current source 701 is provided between the base and collector of the bipolar transistor 702. The constant current source 701 has temperature dependency and allows a current to flow from the base of the bipolar transistor 702 toward the collector.

  The other configuration of the thermal infrared sensor shown in FIG. 10 is the same as the configuration of the thermal infrared sensor shown in FIG. 4, and corresponding portions are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the configuration of the thermal infrared sensor shown in FIG. 10, bipolar transistor 702 conducts when its emitter potential becomes higher than the base potential. Therefore, horizontal drive lines 104a and 104b are supplied with an L level voltage when not selected, and are maintained at an H level voltage level when selected. In the selected pixel (102b), the emitter current Ie flows from the horizontal drive line 104b, and the base current Ib is supplied to the constant current source 701 via the base side node 712. Bipolar transistor 702 causes collector current hfe · Ib to flow to collector side node 710. In the vertical drive line 105, the total current of the current Io and hfe · Ib flows as the current Ic. Therefore, the output voltage generated as output OUT is given by the product of resistance value Rl of load resistance element 403 and current Ic (when ground voltage Vss is 0 V). The output voltage Vout is given by the following equation.

Vout = Ic · Rl
As a relational expression of each current, a relational expression similar to that described in the first to fourth embodiments is obtained, and a highly sensitive temperature sensor can be realized by current amplification of the bipolar transistor 702. Further, in each of the pixels 102a and 102b, support legs for arranging the transistor wiring are support legs for the collector of the bipolar transistor and the common node of the constant current source 701, and a support leg for arranging the wiring for the emitter of the bipolar transistor 702. As in the first to fourth embodiments, the heat insulating characteristics of the support legs can be maintained at the same level as the resistance bolometer and the diode type temperature sensor.

  11A to 11C are diagrams illustrating a configuration of the constant current source 701 illustrated in FIG. In FIG. 11A, constant current source 701 uses an N-channel MOS transistor 715 whose gate and drain are coupled to base side node 712 and whose source is connected to collector side node 710. In this case, the base current Ib flows toward the base side node 712 and the current Io flows toward the collector side node 710. Current Io is a forward saturation current of the MOS transistor, and has temperature dependency similar to that of the first embodiment. By the amplification operation of the bipolar transistor 702, the temperature change is detected by amplifying the temperature change of the current. Thereby, the effect similar to Embodiment 1 can be acquired.

  In FIG. 11B, the constant current source 701 includes a PN junction diode 720 having an anode connected to the collector side node 710 and a cathode connected to the base side node 712. In this case, the temperature is detected using the temperature dependence of the reverse saturation current of the PN junction diode 720 as in the second embodiment.

  In FIG. 11C, a constant current source 701 is formed of a JFET whose gate and drain are connected to a base side node 712 and whose source is connected to a collector side node 710. This JFET may be a PN junction type JFET or a Schottky barrier type JFET (MESFET). Also in this case, as in the fourth embodiment, the base current Ib of the bipolar transistor is allowed to flow as the forward saturation current Io, and the temperature is detected using the temperature dependence of this current.

  Therefore, by utilizing the constant current source 701 shown in FIGS. 11A to 11C, the temperature dependence of the constant current source 701 is amplified by the bipolar transistor 702, and the temperature is detected with high sensitivity. Can be performed.

  Note that in FIGS. 11A and 11C, N-channel transistors are used. However, a P-channel transistor may be used. Further, a Schottky diode may be used instead of the PN junction diode 720 illustrated in FIG. Further, a bipolar transistor connected in Darlington may be used as the bipolar transistor.

  The manufacturing process of the thermal infrared sensor according to the fifth embodiment of the present invention is formed using the same process as the manufacturing process shown in FIGS. 6 (A) to 6 (G). A PNP bipolar transistor and a constant current source are formed in a single crystal silicon layer having an SOI structure.

  The load resistance element 403 may be realized by any of the wiring resistance, the diffusion resistance, and the transistor element in the first to fifth embodiments.

  Also in the fifth embodiment of the present invention, a constant current source for supplying a temperature-dependent current Io and a PNP bipolar transistor for amplifying the current of the constant current source are used as temperature sensors. As in (4) to (4), it is possible to realize a thermal infrared sensor with high sensitivity and small characteristic variation between pixels.

  Further, Embodiments 1 to 5 described so far may be used in appropriate combination.

  The thermal infrared detector and thermal infrared sensor according to the present invention can be applied to various sensor applications to realize a high-sensitivity and small-sized sensor, and is applied to an image sensor, a light receiving device of an infrared remote controller, and the like. can do.

It is a figure which shows roughly the external appearance of the thermal type infrared sensor according to this invention. It is a figure which shows roughly the planar layout of the pixel of the thermal type infrared sensor shown in FIG. FIG. 3 is a diagram schematically showing a cross-sectional structure taken along line 3A-3A shown in FIG. 2. It is a figure which shows the electrical circuit structure of the principal part of the thermal type infrared sensor shown in FIG. It is a figure which shows the equivalent circuit of the selection pixel, and the flowing electric current. (A)-(G) is a figure which shows the manufacturing process of the thermal type infrared sensor according to Embodiment 1 of this invention. It is a figure which shows the electrical equivalent circuit of the pixel according to Embodiment 2 of this invention. It is a figure which shows the electrical equivalent circuit of the pixel of the infrared sensor according to Embodiment 3 of this invention. It is a figure which shows the electrical equivalent circuit of the pixel of the infrared sensor according to Embodiment 4 of this invention. It is a figure which shows the electrical circuit structure of the thermal type infrared sensor according to Embodiment 5 of this invention. (A)-(C) is a figure which shows the specific structure of the constant current source shown in FIG. 10, respectively.

Explanation of symbols

  100 Thermal Infrared Sensor, 101 Silicon Substrate, 102 Pixels, 103 Pixel Array, 104 Horizontal Drive Line, 105 Vertical Drive Line, 106 Vertical Signal Processing Circuit, 107 Horizontal Signal Processing Circuit, 202 Temperature Sensor Unit, 204 Temperature Sensor, 201a, 201b, 201 support legs, 154a, 154b wiring, 205 wiring, 160 isolation region, 102a, 102b pixel, 104a, 104b horizontal drive line, 401 constant current source, 402 bipolar transistor, 403 load resistance, 415 MOS transistor, 601 silicon insulation Film, 602 single crystal silicon layer, 301 infrared absorption structure, 612 etching hole, 03 cavity (recess), 420 diode, 430 JFET, 402a, 402b bipolar transistor, 701 constant current source, 70 2 Bipolar transistor, 715 MOS transistor, 720 diode, 730 JFET.

Claims (8)

A thermal infrared detector coupled between a selection signal line and a readout signal line and detecting a temperature change caused by incident infrared rays,
A transistor element having a control electrode, a first electrode connected to the readout signal line, and a second electrode connected to the selection signal line, and coupled between the control electrode and the readout signal line And a thermal infrared detector comprising a current source for supplying a temperature-dependent current. The transistor element and the current source constitute a sensor unit held by first and second support legs in a cavity formed on a substrate,
The thermal infrared detector further includes:
A first wiring formed on the first support leg and connecting the current source and the first electrode to the read signal line;
The thermal infrared detector according to claim 1, further comprising: a second wiring formed on the second support leg and connecting the second electrode to the selection signal line.   2. The thermal infrared detector according to claim 1, wherein the current source includes any one of a diode-connected field effect transistor that flows a forward saturation current and a diode that flows a reverse saturation current.   4. The thermal infrared detector according to claim 1, wherein the transistor element includes a plurality of bipolar transistors connected in Darlington. 5.   The thermal infrared detector according to claim 2, wherein the sensor unit is formed using a single crystal silicon film formed on an insulating film as a substrate region. A plurality of horizontal drive lines;
A plurality of vertical drive lines;
Each is arranged in a two-dimensional array of rows and columns so as to correspond to the intersections of the horizontal drive lines and the vertical drive lines, and each includes a bipolar transistor element, a base and a collector of the bipolar transistor element, A temperature sensor for detecting a temperature change caused by incident infrared rays disposed in a recess formed on a substrate, and a current source for supplying a current having a temperature dependency connected between the temperature sensor and the temperature sensor. First and second support legs held on the recesses, an infrared absorber thermally coupled to the temperature sensor, a collector of the bipolar transistor element and the current disposed on the first support legs A first wiring for connecting a first electrode of the source to a corresponding vertical drive line; and a second supporting leg disposed on the second support leg, and the emitter of the bipolar transistor element corresponding to a corresponding horizontal drive. And a second wiring connected to the line, a plurality of pixels,
A signal processing circuit for supplying a bias voltage for selecting a pixel for each pixel row, coupled to the plurality of horizontal drive lines, and coupled between each of the vertical drive lines and a power source, A thermal infrared sensor comprising a plurality of load resistance elements that cause a voltage change according to a detection current of a selected pixel in a corresponding column.   The thermal infrared sensor according to claim 6, wherein the current source includes any one of a diode-connected field effect transistor that supplies a forward saturation current and a diode that supplies a reverse saturation current.   The thermal infrared sensor according to claim 6, wherein the bipolar transistor element includes a plurality of bipolar transistors connected in Darlington.

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