WO2022030039A1 - Thermopile sensor - Google Patents

Thermopile sensor Download PDF

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Publication number
WO2022030039A1
WO2022030039A1 PCT/JP2021/007659 JP2021007659W WO2022030039A1 WO 2022030039 A1 WO2022030039 A1 WO 2022030039A1 JP 2021007659 W JP2021007659 W JP 2021007659W WO 2022030039 A1 WO2022030039 A1 WO 2022030039A1
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WO
WIPO (PCT)
Prior art keywords
thermopile
metal
protective film
sensor
metal protective
Prior art date
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PCT/JP2021/007659
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French (fr)
Japanese (ja)
Inventor
隆 笠井
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Ｍｍｉセミコンダクター株式会社
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Publication of WO2022030039A1 publication Critical patent/WO2022030039A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
    • G01F1/69—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
    • G01F1/692—Thin-film arrangements

Definitions

  • the present invention relates to a thermopile type sensor.
  • thermopile type sensor As a kind of thermopile type sensor, a heater arranged in the flow path of the fluid to heat the fluid, a first temperature sensitive element (thermopile) arranged on the upstream side of the flow path with respect to the heater, and a thermopile.
  • a flow rate sensor having a second temperature-sensitive element (thermopile) arranged on the downstream side has been proposed (see, for example, Patent Document 1).
  • thermopile type sensor a first temperature sensitive element (thermopile) and a second temperature sensitive element (thermopile) are arranged so that rows of hot contacts of each other face each other, and a cold contact and a hot contact are arranged.
  • thermopile type sensor a first temperature sensitive element (thermopile) and a second temperature sensitive element (thermopile) are arranged so that rows of hot contacts of each other face each other, and a cold contact and a hot contact are arranged.
  • Infrared sensors that generate an electromotive force in response to a temperature difference are known, and among them, an infrared sensor having a structure in which aluminum wiring is layered on p-type or n-type polycarbonate has also been proposed (for example, non-infrared sensor).
  • Patent Document 1 a first temperature sensitive element (thermopile) and a second temperature sensitive element (thermopile) are arranged so that rows of hot contacts of each other face each other, and a cold contact and a hot contact are arranged.
  • thermopile infrared sensor using stacked double polypeptide silicon layers based on the CMOS process. Journal of Micromechanics and Microengineering 23.6 (2013): 065026.
  • thermopile type sensor as described above is generally required to have high sensitivity at the time of temperature measurement.
  • the sensitivity varies from thermopile to temperature, and the reliability of the sensitivity to temperature decreases.
  • the temperature around the cold contact is different for each thermopile, and the stability of the sensitivity to the temperature may be lowered.
  • the measurement accuracy of the thermopile type sensor is lowered and the productivity is lowered in order to improve the dimensional accuracy of the cavity area.
  • thermopile type sensor in which at least a part of a circuit portion including an integrated circuit is covered with a metal protective film has also been proposed (see Patent Document 2).
  • a thermopile type sensor it is considered that the effect of the electromagnetic shield can be obtained and the resistance to electromagnetic noise can be improved by being covered with the metal protective film.
  • the part related to temperature detection is not covered by the metal protective film, the cold contacts in the thermopile are also warmed when the substrate is warmed by the influence of heat generated from the internal heater and external infrared rays, and the same as above. Problems can occur that reduce the reliability of the sensitivity.
  • the ultimate object of the present invention is to improve the resistance of the thermopile type sensor to electromagnetic noise, or to improve the measurement accuracy or productivity.
  • the present invention for solving the above problems
  • a cavity area which is a recess on the substrate that opens on the predetermined surface side,
  • a thin film portion formed so as to cover the opening of the cavity area,
  • a sensor unit formed on the thin film portion and related to temperature detection, and a sensor portion.
  • a circuit unit formed on a predetermined surface on the substrate and constituting an electric circuit is provided.
  • the sensor unit is composed of a plurality of thermocouples arranged in parallel at predetermined intervals in the thin film unit, and has two or more thermopile arranged side by side. Each of the thermocouples has a warm contact formed at the end closer to the adjacent thermopile and a cold contact formed at the end farther from the adjacent thermopile, the warm contact being the cavity.
  • the cold junction is located on a region of the substrate other than the cavity area.
  • the circuit portion, the cold contact, and a part of the region of the thermopile on the cold contact side that overlaps the cavity area in a plan view are covered with a metal protective film. It is a thermopile type sensor.
  • thermopile type sensor since the thermopile type sensor has a monolithic structure in which a sensor unit and a circuit unit are provided on the same substrate, it is easy to realize a small module, and a complicated signal in the sensor unit is transmitted to the circuit unit. It is possible to process. Further, a hot contact and a cold contact are formed at both ends of the thermocouple, and a temperature difference is generated between them, so that an electromotive force can be generated by the Zeebeck effect. In addition, the circuit section, the cold contact, and a part of the region on the cold contact side of the thermopile that overlaps the cavity area in plan view are covered with a metal protective film, so that they are resistant to electromagnetic noise. It is possible to obtain the effects of improvement, improvement of measurement accuracy of temperature measurement, and improvement of productivity.
  • the metal protective film may be a thermopile type sensor characterized in that it is connected to the ground in the circuit portion. According to this, since the metal protective film is electrically connected to the ground in the circuit portion, it is possible to improve the electromagnetic shielding property.
  • a plurality of metal terminals are formed on the substrate, and the plurality of metal terminals are exposed to the outside through an opening on the thin film portion side, and the plurality of metal terminals of the plurality of metal terminals are exposed to the outside.
  • some metal terminals are connected to the metal protective film, and among the plurality of metal terminals, the metal terminals other than the part of the metal terminals are formed of the metal film and a predetermined signal line of the circuit portion.
  • the metal film may be a thermopile type sensor which is connected to the metal film and has the same thickness as the metal protective film. According to this, since the metal film forming the metal terminal and the metal protective film can be formed in the same process, the manufacturing process can be simplified.
  • thermopile type sensor may be characterized in that the area having a width of 40 ⁇ m or less from the outer periphery of the substrate is not covered by the metal protective film. According to this, laser dicing is applied to the thermopile type sensor when it is made into chips in the manufacturing process, but since the laser cannot be incident from the upper part of the metal protective film, the space not covered by the metal protective film is appropriately spaced. By taking this, laser dicing can be applied.
  • thermopile type sensor is characterized in that the distance from the end of the opening of the cavity area at the end of the partial region on the warm contact side is 5 ⁇ m or more and 100 ⁇ m or less. May be. According to this, it is possible to prevent a problem that may occur when the distance from the end of the opening of the cavity area at the end on the warm contact side of the region is too small or too large. Specifically, when the distance from one end to the other end of the opening of the cavity area is 1000 ⁇ m, and the distance is 0 ⁇ m or more and less than 5 ⁇ m, the dimensional variation of the cavity area occurs. It is difficult to secure a margin.
  • thermopile type sensor it is difficult to keep the distance within 0 ⁇ m or more and less than 5 ⁇ m by etching. Further, if the distance exceeds 100 ⁇ m, the heat of the heater is transmitted to the metal protective film and escapes to the substrate, so that the sensitivity is lowered.
  • the main component of the metal protective film is aluminum, and a surface protective layer containing a silicon-based material is formed on the surface of the metal protective film. It may be a thermopile type sensor characterized in that it is not formed on the plurality of metal terminals.
  • a thermopile type sensor characterized in that it is not formed on the plurality of metal terminals.
  • thermopile type sensor may be characterized in that the main component of the metal protective film is gold. According to this, since gold is less likely to corrode than aluminum, it is possible to eliminate the need to form a surface protective layer. Further, since the electric conductivity and the thermal conductivity are high, it is possible to obtain a higher shielding effect and a higher soaking effect. Gold is also a metal that can be connected to external wiring by wire bonding or the like.
  • the thermopile type sensor may be characterized in that the temperature sensor is provided on the substrate and the temperature sensor is covered with the metal protective film. According to this, it is possible to improve the measurement accuracy by the temperature sensor. Specifically, it is possible to detect the temperature of the cold contact by the temperature sensor. The absolute value of the temperature of the object can be expressed by the sum of the temperature difference between the hot contact and the cold contact and the temperature of the cold contact. Further, since the temperature sensor is covered with a metal protective film, it is difficult for heat from the outside to be transferred to the temperature sensor, and it is suppressed that the temperature sensor itself is heated.
  • the modified example of the present invention is often applied to an infrared sensor.
  • the means for solving the above-mentioned problems can be used in combination as much as possible.
  • thermopile type sensor having a monolithic structure
  • a part of a region on the cold contact side of a circuit portion, a cold contact, and a portion of the thermopile that overlaps the cavity area in a plan view is covered with a metal protective film.
  • thermopile type sensor In this application example, the case where the thermopile type sensor is applied to the thermal type flow rate sensor will be described.
  • the thermopile type sensor according to this application example has a thermopile, and the thermopile is composed of a plurality of thermocouples. Each thermocouple has a hot contact located on the heater side and a cold contact located on the opposite side of the heater and paired with the hot contact.
  • thermocouple In a thermocouple, when the hot contact senses the heat of the heater, an electromotive force is generated due to the temperature difference from the cold contact due to the Seebeck effect. When an electromotive force is generated, it becomes possible to detect the temperature difference between the thermopile and observe the value of the flow rate of the fluid. Here, as the value of the fluid flow rate increases, the value of the temperature difference between the thermopile also increases, and since the two values have individual correlations, the temperature difference between the thermopile can be measured. It becomes possible to acquire the flow rate of the fluid.
  • thermopile is provided symmetrically with the heater in between, and the side where the fluid flows along the flow path when detecting the flow rate is the upstream side, and the opposite side is the downstream side. Further, the thermopile and the heater are arranged on a thin-film insulating film, and a part of the insulating film is formed so as to cover a cavity area which is a recess opened on a predetermined surface side on the substrate.
  • a circuit unit constituting an electronic circuit is provided on the substrate so as to be adjacent to the area where the thermopile, the heater, and the cavity area are located. Since the circuit unit is provided on the substrate, the signal derived from the temperature difference detected by the thermopile can be processed in the vicinity of the thermopile, and the noise immunity can be improved.
  • thermopile type sensor the circuit part is exposed to electromagnetic noise and is affected by the electromagnetic noise, or the temperature distribution is generated on the substrate due to the external environment, so that the cold contact of the thermopile is generated.
  • a temperature difference occurs between the two, or an offset voltage occurs when the size of the cavity area varies.
  • there may be inconveniences such as a decrease in measurement accuracy of the thermopile type sensor and a decrease in productivity in order to improve the dimensional accuracy of the cavity area.
  • thermopile type sensor of the present invention the cold contact located on the region other than the cavity area in the circuit portion and the substrate, and the part of the thermopile on the cold contact side of the portion overlapping the cavity area in a plan view are covered. , Made to be covered by a metal protective film. This makes it possible to improve the above-mentioned drawbacks.
  • thermopile type sensor according to the first embodiment of the present invention will be described in detail with reference to the drawings.
  • the present invention may be applied to another thermopile type sensor such as an infrared sensor.
  • the flow rate sensor according to the present invention is not limited to the following configuration.
  • FIG. 1 is a schematic diagram showing an example of a sensor element 2 constituting the flow rate sensor 1 in this embodiment.
  • the flow sensor 1 is incorporated in, for example, a gas meter, a combustion device, an internal combustion engine such as an automobile, a fuel cell, other industrial devices such as medical care, or an embedded device, and is a thermal type for measuring the amount of fluid passing through a flow path. It is a flow sensor.
  • the flow rate sensor 1 corresponds to the thermopile type sensor in the present invention.
  • FIG. 1 (a) is a perspective view of the sensor element 2 constituting the flow rate sensor 1 in this embodiment
  • FIG. 1 (b) is a cross-sectional view of the cross section XX of FIG. 1 (a).
  • the sensor element 2 includes a heater (heating unit) 3 and a thermopile (temperature detection unit) 4 symmetrically provided with the heater 3 interposed therebetween.
  • the heater 3 is, for example, a resistor made of polysilicon.
  • the shape of the thermopile 4 is substantially rectangular in a plan view.
  • the heater 3 and the thermopile 4 are formed in the insulating thin film 5, and the insulating thin film 5 is provided on the silicon substrate 6.
  • the heater 3 and the thermopile 4 correspond to the sensor unit in the present invention.
  • the insulating thin film 5 and the silicon substrate 6 correspond to the thin film portion and the substrate in the present invention, respectively.
  • the sensor element 2 detects a value indicating the flow rate of the fluid to be measured based on the temperature detection signals output from the two thermopile 4. Specifically, the sensor element 2 calculates the difference between the temperature detection signal output from one thermopile 4 and the temperature detection signal output from the other thermopile 4, and the flow rate of the fluid to be measured is based on the difference. Find the value that indicates. Then, the sensor element 2 outputs a value indicating the flow rate to the electronic circuit unit (described later). Although two thermopile 4s are shown in FIG. 1A, the number of thermopile 4s is not limited as long as they are two or more.
  • each thermopile 4 is configured by arranging a plurality of thermocouples 7 side by side on the insulating thin film 5 at predetermined intervals.
  • the thermocouple 7 per pair has a structure in which a metal thin film is formed on the polysilicon wiring, and the polysilicon wiring is connected to the metal thin film at both ends of the thermocouple 7.
  • the portion connected on the same side as the heater 3 is the hot contact 8, and the portion connected on the opposite side to the heater 3 is the cold contact 9. That is, between the two thermopile 4, the hot contacts 8 are relatively close to each other, and the cold contacts 9 are relatively far from each other.
  • the silicon substrate 6 below the heater 3 and the thermopile 4 on the insulating thin film 5 is provided with a cavity area 10 which is a recess.
  • the hot contacts 8 are located side by side on the upper part of the cavity area 10, and the cold contacts 9 are located in regions other than the cavity area 10 in the silicon substrate 6. Since the heat generated from the heater 3 is discharged to the cavity area 10, the diffusion of the heat generated into the silicon substrate 6 is suppressed. Therefore, the temperature of the cold contact 9 located in the region other than the cavity area 10 of the silicon substrate 6 hardly rises, and the temperature difference from the hot contact 8 located around the heater 3 is more likely to occur. An electromotive force can be efficiently obtained by causing a temperature difference between the hot contact 8 and the cold contact 9.
  • FIG. 2 is a cross-sectional view for explaining the mechanism of the sensor element 2 constituting the flow rate sensor 1 in this embodiment.
  • FIG. 2 schematically shows the temperature distribution when the heater 3 generates heat by the dotted ellipse. It is assumed that the temperature distribution near the heater 3 is higher.
  • FIG. 2A schematically shows an example of the temperature distribution when the heater 3 is energized in a state where no fluid is flowing.
  • FIG. 2B schematically shows an example of the temperature distribution when the heater 3 is energized while the fluid is flowing in the direction of the dotted arrow.
  • the heater 3 and the thermopile 4 are arranged side by side in the sensor element 2 along the direction of the dotted arrow. The longitudinal direction of each of the heater 3 and the thermopile 4 is orthogonal to the flow direction of the fluid.
  • the heat of the heater 3 diffuses symmetrically around the heater 3. Therefore, in the direction of FIG. 2A, the temperature of the temperature contact 8 on the left side of the heater 3 and the temperature of the temperature contact 8 on the right side of the heater 3 are the same. That is, the output voltage of the thermopile 4 does not occur.
  • the heat of the heater 3 is affected by the flow of the fluid and does not diffuse symmetrically around the heater 3, but diffuses asymmetrically along the flow of the fluid. Therefore, in the direction of FIG. 2B, there is a difference between the temperature of the temperature contact 8 on the left side of the heater 3 and the temperature of the temperature contact 8 on the right side of the heater 3.
  • thermopile 4 in proportion to the temperature difference. Further, since the temperature difference increases according to the flow velocity, the magnitude of the flow velocity can be detected based on the electromotive force of the thermopile 4. Further, depending on the flow direction of the fluid, the positive and negative of the temperature difference between the two temperature contacts 8 shown in FIG. 2 (b) are reversed, and the positive and negative of the electromotive force are also reversed, so that the flow direction of the fluid can be detected.
  • the sensor element 2 outputs a value indicating a flow rate by utilizing such a bias in the heat distribution of the heater 3.
  • the output voltage ⁇ V of the sensor element 2 is expressed by, for example, the following equation (1).
  • Th is the temperature of the heater 3
  • Ta is the temperature measured by the ambient temperature sensor provided on the outside of the thermopile 4
  • V f is the average value of the flow velocity
  • a and b are predetermined constants.
  • FIG. 3 is a perspective view showing an example of the flow rate sensor 1 in this embodiment.
  • the flow rate sensor 1 has a monolithic structure in which the sensor element 2 and the electronic circuit unit 11 constituting the circuit are provided on the same chip.
  • FIG. 3 briefly shows a part of the structure of the sensor element 2, that is, the structure around the heater 3 and the thermopile 4. Moreover, the thermopile 4 is also shown briefly.
  • the insulating thin film 5 is formed so as to cover the upper surface of the cavity area 10 and the upper surface of the silicon substrate 6 on which the electronic circuit portion 11 is formed.
  • the structure shown in FIG. 3 includes a metal protective film 12. In FIG.
  • the dotted line R and the dotted line S represent the boundary between the metal protective film 12, and the region surrounded by the dotted line R and the dotted line S is a metal. It represents the area covered by the protective film 12. Due to the thermal conductivity of the metal protective film 12, a soaking effect on heat from the outside of the flow rate sensor 1 and the electric circuit portion 11 can be obtained. Since the electronic circuit portion 11 is formed below the metal protective film 12 and is invisible on the surface of the chip, it is shown by a substantially rectangular dotted line in FIG.
  • the area with a width of 0 ⁇ m or more and 40 ⁇ m or less from the edge of the flow rate sensor 1 is not covered by the metal protective film. That is, the value of W in FIG. 3 is at least 40 ⁇ m.
  • Laser dicing is applied to the flow sensor 1 when it is made into chips in the manufacturing process, but since the laser cannot be incident on the portion covered by the metal protective film 12 from above, a space not covered by the metal protective film 12 is created. It is necessary to take it moderately.
  • the structure shown in FIG. 3 includes metal terminals 13a to 13e.
  • the metal terminals 13a to 13e are exposed to the outside through an opening on the insulating thin film 5 side, and can be connected to the external terminal.
  • the metal terminals 13a, 13b, 13d and 13e are terminals for input / output of the electronic circuit unit 11 and the like, and are not connected to the metal protective film 12.
  • the electronic circuit unit 12 is formed under the metal protective film 12 between the arrangement of the metal terminals 13a to 13e and the thermopile 4 on the near side of the metal terminals 13a to 13e. , It may be formed in other parts. For example, it may be formed in the lower portion of the metal protective film 12 around the cavity area 10. Further, the area around the metal terminals 13a, 13b, 13d and 13e may not be covered by the metal protective film 12.
  • FIG. 4 is a cross-sectional view for explaining a schematic configuration of an example of the flow rate sensor 1 shown in FIG. 4 (a) is a cross-sectional view according to the cross section YY of FIG. 3, and FIG. 4 (b) is a cross-sectional view of the cross section ZZ of FIG.
  • FIG. 4B the silicon substrate 6 at the lower part of the electronic circuit unit 11 is not shown, and the upper part of the silicon substrate 6 is enlarged in the vertical direction.
  • the electronic circuit unit 11, the cold contact 9, and a part of the thermocouple 7 on the cold contact 9 side that overlaps the cavity area 10 in a plan view are formed by the metal protective film 12. Is covered by.
  • the electronic circuit unit 11 corresponds to the circuit unit in the present invention.
  • the distance from one end of the opening of the cavity area 10 to the other end is 1000 ⁇ m.
  • the distance at which the thermocouple 7 is covered by the metal protective film 12 from the end of the opening of the cavity area 10 in the direction from the cold contact 9 side to the warm contact 8 side that is, the value D in FIG. 4A is It is 5 ⁇ m or more and 100 ⁇ m or less.
  • the value of D in FIG. 4A is less than 5 ⁇ m, when the size of the cavity area 10 varies, the portion of the thermocouple 7 that overlaps with the cavity area 10 in a plan view is formed by the metal protective film 12. May not be covered by.
  • the main component of the metal of the metal protective film 12 is aluminum or gold.
  • the main component is aluminum, aluminum is relatively inexpensive among metals, so that the manufacturing cost can be suppressed, and aluminum is a metal generally used when forming the electronic circuit portion 11. Therefore, the metal protective film 12 can be easily formed.
  • aluminum has a relatively high ionization tendency among metals and is easily corroded. Therefore, when used as the main component of the metal protective film 12, it is necessary to form a surface protective layer containing a silicon-based material on the surface.
  • the surface protective layer is not formed on the metal film constituting the metal terminals 13a, 13b, 13d and 13e, or on the metal protective film 12 in the metal terminal 13.
  • the main component is gold, it is not necessary to form a surface protective layer because gold has high corrosion resistance.
  • the main component of the metal film constituting the metal terminals 13a, 13b, 13d and 13e is also gold in accordance with the main component of the metal protective film 12.
  • the cross-sectional view of FIG. 4B shows the configuration of the insulating thin film 5, the electronic circuit portion 11, the metal protective film 12, and the metal terminals 13a to 13e.
  • the metal terminals 13a to 13e are exposed to the outside through the opening on the insulating thin film 5 side.
  • the metal terminal 13c is electrically connected to the metal protective film 12.
  • the metal terminals 13a, 13b, 13d and 13e are electrically connected to a predetermined signal line of the electronic circuit unit 11 formed in the lower part of the metal protective film 12.
  • the predetermined signal line includes an input / output line, a power supply, and a ground.
  • the thickness T of the metal protective film 12 is equal to the thicknesses T1 to T4 of the metal films constituting the metal terminals 13a, 13b, 13d and 13e.
  • FIG. 5 is a perspective view showing a modified example of the flow rate sensor 1 shown in FIG.
  • FIG. 5 briefly shows a part of the structure of the sensor element 2, that is, the structure around the heater 3 and the thermopile 4.
  • the thermopile 4 is also shown briefly.
  • the arrangement angles of the heater 3, the thermopile 4, and the cavity area 10 are different by 90 degrees.
  • the points having a monolithic structure, the point that the region surrounded by the dotted line R and the dotted line S is covered by the metal protective film 12, and the point that the metal terminals 13a to 13e are formed are the same.
  • the cold contact 9 is formed at a position farther from the electronic circuit unit 11 as compared with the configuration shown in FIG. 3, the cold contact 9 is affected by the heat generated by the electronic circuit unit 11. It is difficult, and it is difficult for a temperature difference to occur between the cold contacts 9 in the two pairs of thermopile 4. Further, in the configuration shown in FIG. 5, the direction in which the heater 3 and the thermopile 4 are arranged is rotated by 90 degrees as compared with the configuration shown in FIG. 3, and the direction in which the flow rate is detected is the lateral direction of the chip 1. .. As a result, the fluid to be measured is less likely to receive turbulence of the air flow due to wire bonding connected to the metal terminals 13a to 13e, and the detectability of the flow rate is improved. The configuration shown in FIG. 5 can be actually designed.
  • Example 2 Next, Example 2 of the present invention will be described. In the first embodiment, an example in which the thermopile type sensor is applied to the flow rate sensor 1 has been described, but in this embodiment, an example in which the thermopile type sensor is applied to the infrared sensor will be described.
  • FIG. 6 is a cross-sectional view for explaining a schematic configuration of the infrared sensor 15 in this embodiment. Since the basic configuration is similar to the flow rate sensor 1, the plan view is omitted. Compared to the cross-sectional view of FIG. 4 (a), FIG. 6 does not include the heater 3. Further, if necessary, an infrared absorber film or an infrared absorber is applied to the area of the hot contact 8 of the thermocouple 7, but it is omitted in FIG. As a heat source, infrared rays are irradiated from the outside in the direction of the arrow in FIG. 6, and the thermocouple 7 is heated.
  • the range exposed to infrared rays is wide due to external irradiation, most of the silicon substrate 6 is covered by the metal protective film 12 to prevent infrared rays from being incident on the silicon substrate 6, so that the temperature rise of the silicon substrate 6 is suppressed. .. Further, since the cold contact 9 is covered by the metal protective film 12, but the warm contact 8 is not covered, it is possible to generate a larger temperature difference between the hot contact 8 and the cold contact 9 by irradiating infrared rays. Is.
  • the temperature sensor 14 is provided on the silicon substrate 6 between the electronic circuit unit 11 and the cold contact 9.
  • the temperature sensor 14 can measure the ambient temperature.
  • the ambient temperature represents the temperature of the cold contact 9 in the vicinity of the temperature sensor 14.
  • the temperature sensor 14 when the temperature sensor 14 is provided, the heat conductivity between the cold contact 9 and the temperature sensor 14 is improved by being covered with the metal protective film 12, the temperature around these is made uniform, and the temperature of T is increased. It is possible to reduce the error of the calculated value. Further, since the temperature sensor 14 is covered with the metal protective film 12, it is possible to prevent the temperature sensor 14 from being heated by irradiation with infrared rays. Since the temperature sensor 14 functions as a part of the electronic circuit, it may be built in the electronic circuit unit 11 as a portion constituting the electronic circuit unit 11.
  • the electronic circuit unit 11 may not be formed on the silicon substrate 6 but may be formed outside the area of the silicon substrate 6. In this configuration, only the temperature sensor 14 will be covered by the metal protective film 12. In this case, it is possible that the temperature sensor 14 corresponds to the circuit unit.
  • the temperature sensor 14 includes types such as a resistance change type, a diode type, and a thermistor. Further, in this embodiment, an example in which the temperature sensor 14 is applied to the infrared sensor 15 is shown, but the temperature sensor 14 may be applied to the flow rate sensor 1.
  • ⁇ Invention 1> Cavity area (10), which is a recess opened on the predetermined surface side on the substrate (6), and A thin film portion (5) formed so as to cover the opening of the cavity area, A sensor unit (4) formed in the thin film portion and related to temperature detection, and A circuit unit (11) formed on a predetermined surface on the substrate and constituting an electric circuit is provided.
  • the sensor unit comprises a plurality of thermocouples (7) arranged in parallel at predetermined intervals in the thin film unit, and has two or more thermopile (4) arranged side by side.
  • thermocouples has a warm contact (8) formed at the end near the adjacent thermopile and a cold contact (9) formed at the end far from the adjacent thermopile.
  • the thermocouple is located on the cavity area and the cold junction is located on a region of the substrate other than the cavity area.
  • the circuit portion, the cold contact, and a part of the region of the thermopile on the cold contact side that overlaps the cavity area in a plan view are covered with a metal protective film (12). do, Thermopile type sensor (1).
  • Flow sensor 2 Sensor element 3: Heater 4: Thermopile 5: Insulating thin film 6: Silicon substrate 7: Thermocouple 8: Warm contact 9: Cold contact 10: Cavity area 11: Electronic circuit unit 12: Metal protective film 13a- 13e: Metal terminal 14: Temperature sensor 15: Infrared sensor

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Abstract

This thermopile sensor comprises a substrate, a cavity area, a thin-film part, a sensor part, and a circuit part. The sensor part comprises two or more thermopiles that are arranged side by side and each comprises a plurality of thermocouples arranged on the thin-film part in parallel at a prescribed interval. Each thermocouple comprises a hot junction formed on the end closer to the adjacent thermopile and a cold junction formed on the end further from the adjacent thermopile. The hot junctions are positioned over the cavity area and the cold junctions are positioned over an area of the substrate other than the cavity area. The circuit part, the cold junctions, and portions of the areas of the thermopiles that are on the sides of the cold junctions and overlap with the cavity area in a plan view are covered with a metallic protective film.

Description

サーモパイル型センサThermopile type sensor
　本発明は、サーモパイル型センサに関する。 The present invention relates to a thermopile type sensor.
　従来より、サーモパイル型センサの一種として、流体の流れる流路に配置されて流体を加熱するヒータと、ヒータに対して流路の上流側に配置された第１の感温素子(サーモパイル)、及び下流側に配置された第２の感温素子(サーモパイル)とを有する流量センサが提案されていた（例えば、特許文献１参照）。 Conventionally, as a kind of thermopile type sensor, a heater arranged in the flow path of the fluid to heat the fluid, a first temperature sensitive element (thermopile) arranged on the upstream side of the flow path with respect to the heater, and a thermopile. A flow rate sensor having a second temperature-sensitive element (thermopile) arranged on the downstream side has been proposed (see, for example, Patent Document 1).
　また、サーモパイル型センサとしては、第１の感温素子(サーモパイル)及び第２の感温素子(サーモパイル)を、互いの温接点の列どうしが対向するように配置し、冷接点と温接点の温度差に応じて起電力を生じさせる赤外線センサが公知であり、その中には、ｐ型またはｎ型のポリシリコンにアルミニウム配線を重ねた構造を有する赤外線センサも提案されている（例えば、非特許文献１）。 Further, as a thermopile type sensor, a first temperature sensitive element (thermopile) and a second temperature sensitive element (thermopile) are arranged so that rows of hot contacts of each other face each other, and a cold contact and a hot contact are arranged. Infrared sensors that generate an electromotive force in response to a temperature difference are known, and among them, an infrared sensor having a structure in which aluminum wiring is layered on p-type or n-type polycarbonate has also been proposed (for example, non-infrared sensor). Patent Document 1).
特許第５１１２７２８号公報Japanese Patent No. 5112728 欧州特許出願公開第１０９２９６２号明細書European Patent Application Publication No. 1092962 欧州特許出願公開第２９３０４７５号明細書European Patent Application Publication No. 2930475 特許第５８６１４９７号公報Japanese Patent No. 5861497
　上記のようなサーモパイル型センサにおいては、一般的に、温度測定時において高感度であることが求められる。しかしながら、例えば、サーモパイルの下部に形成された、基板上の所定面側に開口した凹部であるキャビティエリアの寸法のバラツキが原因でサーモパイルごとに感度に差が生じ、温度に対する感度の信頼性が低下する場合があった。また、外部環境が原因で基板上に温度分布が生じると、サーモパイルごとに冷接点周辺の温度に差が生じ、温度に対する感度の安定性が低下する場合があった。その結果、サーモパイル型センサの測定精度が低下したり、キャビティエリアの寸法精度を向上させるために生産性が低下したりする不都合があった。 The thermopile type sensor as described above is generally required to have high sensitivity at the time of temperature measurement. However, for example, due to the variation in the dimensions of the cavity area, which is a recess formed on the lower part of the thermopile and opened on the predetermined surface side, the sensitivity varies from thermopile to temperature, and the reliability of the sensitivity to temperature decreases. There was a case. Further, when a temperature distribution is generated on the substrate due to the external environment, the temperature around the cold contact is different for each thermopile, and the stability of the sensitivity to the temperature may be lowered. As a result, there are inconveniences that the measurement accuracy of the thermopile type sensor is lowered and the productivity is lowered in order to improve the dimensional accuracy of the cavity area.
　これに対し、集積回路を含む回路部の少なくとも一部分が、金属保護膜によりカバーされているサーモパイル型センサも提案されている（特許文献２参照）。このようなサーモパイル型センサでは、金属保護膜によりカバーされていることにより、電磁シールドの効果が得られ、電磁ノイズへの耐性も向上することが考えられる。しかし、温度検出に係る部分が金属保護膜によりカバーされていないため、内部のヒータや外部の赤外線等からの発熱の影響で、基板が温められる際にサーモパイルにおける冷接点も温められ、上記同様、感度の信頼性が低下する問題が生じ得る。 On the other hand, a thermopile type sensor in which at least a part of a circuit portion including an integrated circuit is covered with a metal protective film has also been proposed (see Patent Document 2). In such a thermopile type sensor, it is considered that the effect of the electromagnetic shield can be obtained and the resistance to electromagnetic noise can be improved by being covered with the metal protective film. However, since the part related to temperature detection is not covered by the metal protective film, the cold contacts in the thermopile are also warmed when the substrate is warmed by the influence of heat generated from the internal heater and external infrared rays, and the same as above. Problems can occur that reduce the reliability of the sensitivity.
　本発明では、サーモパイル型センサの電磁ノイズへの耐性の向上を図ること、あるいは、測定精度または生産性の向上を図ることを最終的な目的とする。 The ultimate object of the present invention is to improve the resistance of the thermopile type sensor to electromagnetic noise, or to improve the measurement accuracy or productivity.
　上記の課題を解決するための本発明は、
　基板上の所定面側に開口した凹部であるキャビティエリアと、
　前記キャビティエリアの開口を覆うように形成された薄膜部と、
　前記薄膜部に形成され、温度の検出に係るセンサ部と、
　前記基板上の所定面に形成され、電気回路を構成する回路部と、を備え、
　前記センサ部は、前記薄膜部に所定の間隔で並列して配置される複数の熱電対から成り、並んで配置される二つ以上のサーモパイルを有し、
　前記熱電対の各々は、隣のサーモパイルに近い側の端部に形成された温接点、及び前記隣のサーモパイルに遠い側の端部に形成された冷接点を有し、前記温接点は前記キャビティエリア上に位置し、前記冷接点は前記基板における前記キャビティエリア以外の領域上に位置し、
　前記回路部と、前記冷接点と、前記サーモパイルにおいて平面視で前記キャビティエリアと重なる部分の前記冷接点側の一部の領域とが、金属保護膜によりカバーされていることを特徴とする、
　サーモパイル型センサである。 The present invention for solving the above problems
A cavity area, which is a recess on the substrate that opens on the predetermined surface side,
A thin film portion formed so as to cover the opening of the cavity area,
A sensor unit formed on the thin film portion and related to temperature detection, and a sensor portion.
A circuit unit formed on a predetermined surface on the substrate and constituting an electric circuit is provided.
The sensor unit is composed of a plurality of thermocouples arranged in parallel at predetermined intervals in the thin film unit, and has two or more thermopile arranged side by side.
Each of the thermocouples has a warm contact formed at the end closer to the adjacent thermopile and a cold contact formed at the end farther from the adjacent thermopile, the warm contact being the cavity. Located on the area, the cold junction is located on a region of the substrate other than the cavity area.
The circuit portion, the cold contact, and a part of the region of the thermopile on the cold contact side that overlaps the cavity area in a plan view are covered with a metal protective film.
It is a thermopile type sensor.
　本発明によれば、該サーモパイル型センサが、同一基板上にセンサ部と回路部を設けたモノリシック構造を有するため、小型のモジュールを実現しやすく、且つ、センサ部における複雑な信号を回路部において処理することが可能である。また、熱電対の両端部にそれぞれ温接点と冷接点が形成され、それらの間に温度差を生じさせることで、ゼーベック効果により、起電力を生じさせることが可能である。また、回路部と、冷接点と、サーモパイルにおいて平面視でキャビティエリアと重なる部分の冷接点側の一部の領域とが、金属保護膜によりカバーされていることにより、それぞれ電磁ノイズへの耐性の向上、温度測定の測定精度向上、及び生産性の向上を効果として得られる。 According to the present invention, since the thermopile type sensor has a monolithic structure in which a sensor unit and a circuit unit are provided on the same substrate, it is easy to realize a small module, and a complicated signal in the sensor unit is transmitted to the circuit unit. It is possible to process. Further, a hot contact and a cold contact are formed at both ends of the thermocouple, and a temperature difference is generated between them, so that an electromotive force can be generated by the Zeebeck effect. In addition, the circuit section, the cold contact, and a part of the region on the cold contact side of the thermopile that overlaps the cavity area in plan view are covered with a metal protective film, so that they are resistant to electromagnetic noise. It is possible to obtain the effects of improvement, improvement of measurement accuracy of temperature measurement, and improvement of productivity.
　また、本発明においては、前記金属保護膜は、前記回路部におけるグランドに接続されていることを特徴とする、サーモパイル型センサとしてもよい。これによれば、金属保護膜が回路部におけるグランドに電気的に接続されるため、電磁シールド性を向上させることが可能である。 Further, in the present invention, the metal protective film may be a thermopile type sensor characterized in that it is connected to the ground in the circuit portion. According to this, since the metal protective film is electrically connected to the ground in the circuit portion, it is possible to improve the electromagnetic shielding property.
　また、本発明においては、前記基板上には、複数の金属端子が形成されており、前記複数の金属端子は、前記薄膜部側の開口を通じて外部に露出しており、前記複数の金属端子のうち、一部の金属端子は、前記金属保護膜に接続され、前記複数の金属端子のうち、上記一部の金属端子以外の金属端子は、金属膜により形成され前記回路部の所定の信号線に接続されており、前記金属膜は、前記金属保護膜と、同じ厚さであることを特徴とする、サーモパイル型センサとしてもよい。これによれば、金属端子を形成する金属膜と、金属保護膜とを、同じ工程で形成することが可能であるため、製造工程を簡略化することが可能である。 Further, in the present invention, a plurality of metal terminals are formed on the substrate, and the plurality of metal terminals are exposed to the outside through an opening on the thin film portion side, and the plurality of metal terminals of the plurality of metal terminals are exposed to the outside. Among them, some metal terminals are connected to the metal protective film, and among the plurality of metal terminals, the metal terminals other than the part of the metal terminals are formed of the metal film and a predetermined signal line of the circuit portion. The metal film may be a thermopile type sensor which is connected to the metal film and has the same thickness as the metal protective film. According to this, since the metal film forming the metal terminal and the metal protective film can be formed in the same process, the manufacturing process can be simplified.
　また、本発明においては、前記基板の外周から４０μm以下の幅のエリアは、前記金属保護膜によりカバーされないことを特徴とする、サーモパイル型センサとしてもよい。これによれば、該サーモパイル型センサは製造工程において、チップ化する際にレーザーダイシングが適用されるが、金属保護膜の上部からはレーザーが入射できないため、金属保護膜によりカバーされないスペースを適度にとることで、レーザーダイシングの適用が可能となる。 Further, in the present invention, the thermopile type sensor may be characterized in that the area having a width of 40 μm or less from the outer periphery of the substrate is not covered by the metal protective film. According to this, laser dicing is applied to the thermopile type sensor when it is made into chips in the manufacturing process, but since the laser cannot be incident from the upper part of the metal protective film, the space not covered by the metal protective film is appropriately spaced. By taking this, laser dicing can be applied.
　また、本発明においては、前記一部の領域の前記温接点側の端部における、前記キャビティエリアの開口部の端からの距離は、５μm以上１００μm以下であることを特徴とする、サーモパイル型センサとしてもよい。これによれば、該領域の温接点側の端部における、キャビティエリアの開口部の端からの距離が小さすぎる場合や大きすぎる場合に生じ得る問題点を防止することが可能である。具体的には、キャビティエリアの開口部の一方の端からもう一方の端までの距離を１０００μmとする場合、該距離が０μm以上５μm未満であると、キャビティエリアの寸法のバラツキが生じた場合にマージンを確保することが困難である。且つ、該サーモパイル型センサの製造工程において、エッチングにより該距離を０μm以上５μm未満に収めることは困難である。また、該距離が１００μm超過であると、ヒータの熱が金属保護膜を伝達して基板に逃げてしまうため、感度が低下してしまう。 Further, in the present invention, the thermopile type sensor is characterized in that the distance from the end of the opening of the cavity area at the end of the partial region on the warm contact side is 5 μm or more and 100 μm or less. May be. According to this, it is possible to prevent a problem that may occur when the distance from the end of the opening of the cavity area at the end on the warm contact side of the region is too small or too large. Specifically, when the distance from one end to the other end of the opening of the cavity area is 1000 μm, and the distance is 0 μm or more and less than 5 μm, the dimensional variation of the cavity area occurs. It is difficult to secure a margin. Moreover, in the manufacturing process of the thermopile type sensor, it is difficult to keep the distance within 0 μm or more and less than 5 μm by etching. Further, if the distance exceeds 100 μm, the heat of the heater is transmitted to the metal protective film and escapes to the substrate, so that the sensitivity is lowered.
　また、本発明においては、前記金属保護膜の主成分は、アルミニウムであり、前記金属保護膜の表面には、シリコン系の材質を含む表面保護層が形成されており、前記表面保護層は、前記複数の金属端子上には形成されないことを特徴とする、サーモパイル型センサとしてもよい。これによれば、アルミニウムは、金属の中でも比較的安価であるため、製造コストを抑えることが可能であり、且つ、集積回路を形成する際に一般的に用いられる金属であるため、製造が容易である。そして、アルミニウムは、金属の中でも比較的イオン化傾向が大きく、腐食しやすいが、表面保護層により腐食を防止することができる。さらに、金属端子上には表面保護層は形成されないため、外部配線と金属端子の接続性を確保することができる。 Further, in the present invention, the main component of the metal protective film is aluminum, and a surface protective layer containing a silicon-based material is formed on the surface of the metal protective film. It may be a thermopile type sensor characterized in that it is not formed on the plurality of metal terminals. According to this, since aluminum is relatively inexpensive among metals, it is possible to suppress the manufacturing cost, and since it is a metal generally used when forming an integrated circuit, it is easy to manufacture. Is. Aluminum has a relatively high ionization tendency among metals and is easily corroded, but the surface protective layer can prevent corrosion. Further, since the surface protective layer is not formed on the metal terminal, the connectivity between the external wiring and the metal terminal can be ensured.
　また、本発明においては、前記金属保護膜の主成分は、金であることを特徴とする、サーモパイル型センサとしてもよい。これによれば、金はアルミニウムと比較して腐食しにくいため、表面保護層の形成を不要とすることが可能である。また、電気伝導率や熱伝導率が高いため、より高いシールド効果及び、より高い均熱効果を得ることが可能である。そして、金はワイヤボンディングなどによる外部配線の接続が可能な金属でもある。 Further, in the present invention, the thermopile type sensor may be characterized in that the main component of the metal protective film is gold. According to this, since gold is less likely to corrode than aluminum, it is possible to eliminate the need to form a surface protective layer. Further, since the electric conductivity and the thermal conductivity are high, it is possible to obtain a higher shielding effect and a higher soaking effect. Gold is also a metal that can be connected to external wiring by wire bonding or the like.
　また、本発明の変形例においては、前記基板上に温度センサを備え、前記温度センサは、前記金属保護膜によりカバーされていることを特徴とする、サーモパイル型センサとしてもよい。これによれば、温度センサによって、測定精度を高めることが可能である。具体的には、温度センサによって、冷接点の温度を検出することが可能である。対象物の温度の絶対値は、温接点と冷接点の間の温度差と、冷接点の温度との和で表すことが可能である。また、温度センサは金属保護膜によりカバーされているため、外部からの熱が温度センサに伝達されづらく、温度センサ自体が温められることが抑制される。なお、本発明の変形例は赤外線センサに適用されることが多い。 Further, in the modification of the present invention, the thermopile type sensor may be characterized in that the temperature sensor is provided on the substrate and the temperature sensor is covered with the metal protective film. According to this, it is possible to improve the measurement accuracy by the temperature sensor. Specifically, it is possible to detect the temperature of the cold contact by the temperature sensor. The absolute value of the temperature of the object can be expressed by the sum of the temperature difference between the hot contact and the cold contact and the temperature of the cold contact. Further, since the temperature sensor is covered with a metal protective film, it is difficult for heat from the outside to be transferred to the temperature sensor, and it is suppressed that the temperature sensor itself is heated. The modified example of the present invention is often applied to an infrared sensor.
　なお、本発明においては、上記した課題を解決するための手段は、可能なかぎり組み合わせて使用することが可能である。 In the present invention, the means for solving the above-mentioned problems can be used in combination as much as possible.
　本発明によれば、モノリシック構造を有するサーモパイル型センサにおいて、回路部、及び冷接点、及びサーモパイルにおいて平面視でキャビティエリアと重なる部分の冷接点側の一部の領域が金属保護膜によりカバーされることにより、それぞれ電磁ノイズへの耐性の向上、及び流体の流量の測定誤差の低減、及び生産性の向上を実現することが可能である。 According to the present invention, in a thermopile type sensor having a monolithic structure, a part of a region on the cold contact side of a circuit portion, a cold contact, and a portion of the thermopile that overlaps the cavity area in a plan view is covered with a metal protective film. Thereby, it is possible to improve the resistance to electromagnetic noise, reduce the measurement error of the fluid flow rate, and improve the productivity, respectively.
実施例における流量センサを構成するセンサ素子の一例を示す模式的な図である。It is a schematic diagram which shows an example of the sensor element which constitutes the flow rate sensor in an Example. 実施例における流量センサを構成するセンサ素子の仕組みを説明するための断面図である。It is sectional drawing for demonstrating the mechanism of the sensor element constituting the flow rate sensor in an Example. 実施例における流量センサの一例を示す斜視図である。It is a perspective view which shows an example of the flow rate sensor in an Example. 図３に示す流量センサの一例の概略構成を説明するための断面図である。It is sectional drawing for demonstrating the schematic structure of the example of the flow rate sensor shown in FIG. 図３に示す流量センサの変形例を示す斜視図である。It is a perspective view which shows the modification of the flow rate sensor shown in FIG. 実施例における赤外線センサの概略構成を説明するための断面図である。It is sectional drawing for demonstrating the schematic structure of the infrared sensor in an Example.
〔適用例〕
　本適用例においては、サーモパイル型センサを熱式の流量センサに適用した場合について説明する。本適用例に係るサーモパイル型センサはサーモパイルを有し、サーモパイルは複数の熱電対から構成される。各々の熱電対は、ヒータ側に位置する温接点、及びヒータと反対側に位置し、温接点と対を成す冷接点を備えている。 [Application example]
In this application example, the case where the thermopile type sensor is applied to the thermal type flow rate sensor will be described. The thermopile type sensor according to this application example has a thermopile, and the thermopile is composed of a plurality of thermocouples. Each thermocouple has a hot contact located on the heater side and a cold contact located on the opposite side of the heater and paired with the hot contact.
　熱電対は、温接点がヒータの熱を感知すると、ゼーベック効果により、冷接点との温度差によって起電力が生じる。起電力が生じると、サーモパイルの間の温度差の検知が可能となり、流体の流量の値を観測することが可能となる。ここで、流体の流量の値が増大するほど、サーモパイルの間の温度差の値も増大し、両者の値は個々に相関性を持っているため、サーモパイルの間の温度差を測定することで流体の流量を取得することが可能となる。 In a thermocouple, when the hot contact senses the heat of the heater, an electromotive force is generated due to the temperature difference from the cold contact due to the Seebeck effect. When an electromotive force is generated, it becomes possible to detect the temperature difference between the thermopile and observe the value of the flow rate of the fluid. Here, as the value of the fluid flow rate increases, the value of the temperature difference between the thermopile also increases, and since the two values have individual correlations, the temperature difference between the thermopile can be measured. It becomes possible to acquire the flow rate of the fluid.
　サーモパイルはヒータを挟んで対称に設けられており、流量検出の際に流体が流路に沿って流れてくる側を上流側、反対側を下流側としている。また、サーモパイルとヒータは、薄膜状の絶縁膜上に配置されており、絶縁膜の一部は基板上の所定面側に開口した凹部であるキャビティエリアを覆うように形成されている。 The thermopile is provided symmetrically with the heater in between, and the side where the fluid flows along the flow path when detecting the flow rate is the upstream side, and the opposite side is the downstream side. Further, the thermopile and the heater are arranged on a thin-film insulating film, and a part of the insulating film is formed so as to cover a cavity area which is a recess opened on a predetermined surface side on the substrate.
　サーモパイル、及びヒータ、及びキャビティエリアが位置するエリアに隣接するように、電子回路を構成する回路部が基板上に設けられている。回路部が基板上に設けられていることにより、サーモパイルが検知した温度差に由来する信号をサーモパイルの近傍において処理でき、ノイズ耐性を向上させることが可能である。 A circuit unit constituting an electronic circuit is provided on the substrate so as to be adjacent to the area where the thermopile, the heater, and the cavity area are located. Since the circuit unit is provided on the substrate, the signal derived from the temperature difference detected by the thermopile can be processed in the vicinity of the thermopile, and the noise immunity can be improved.
　しかし、上記のサーモパイル型センサにおいては、回路部が電磁ノイズに対して晒されていることで電磁ノイズの影響を受ける、あるいは外部環境が原因で基板上に温度分布が生じることでサーモパイルの冷接点どうしの間で温度差が生じる、あるいはキャビティエリアの寸法のバラツキが生じた際にオフセット電圧が生じるといった欠点が考えられる。結果、サーモパイル型センサの測定精度が低下したり、キャビティエリアの寸法精度を向上させるために生産性が低下したりする不都合が生じ得る。 However, in the above thermopile type sensor, the circuit part is exposed to electromagnetic noise and is affected by the electromagnetic noise, or the temperature distribution is generated on the substrate due to the external environment, so that the cold contact of the thermopile is generated. There may be a drawback that a temperature difference occurs between the two, or an offset voltage occurs when the size of the cavity area varies. As a result, there may be inconveniences such as a decrease in measurement accuracy of the thermopile type sensor and a decrease in productivity in order to improve the dimensional accuracy of the cavity area.
　そこで、本発明におけるサーモパイル型センサについては、回路部、及び基板におけるキャビティエリア以外の領域上に位置する冷接点、及びサーモパイルにおいて平面視でキャビティエリアと重なる部分の冷接点側の一部の領域が、金属保護膜によりカバーされるようにした。このことで、上記の欠点を改善することが可能となる。 Therefore, in the thermopile type sensor of the present invention, the cold contact located on the region other than the cavity area in the circuit portion and the substrate, and the part of the thermopile on the cold contact side of the portion overlapping the cavity area in a plan view are covered. , Made to be covered by a metal protective film. This makes it possible to improve the above-mentioned drawbacks.
〔実施例１〕
　以下、本発明の実施例１に係るサーモパイル型センサについて、図面を用いて詳細に説明する。なお、以下の実施形態においては、本発明を流量センサに適用した例について説明するが、本発明を赤外線センサ等、他のサーモパイル型センサに適用しても構わない。なお、本発明に係る流量センサは、以下の構成には限定されない。 [Example 1]
Hereinafter, the thermopile type sensor according to the first embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, an example in which the present invention is applied to a flow rate sensor will be described, but the present invention may be applied to another thermopile type sensor such as an infrared sensor. The flow rate sensor according to the present invention is not limited to the following configuration.
＜装置構成＞ <Device configuration>
　図１は、本実施例における流量センサ１を構成するセンサ素子２の一例を示す模式的な図である。流量センサ１は、例えばガスメータや燃焼機器、自動車等の内燃機関、燃料電池、その他医療等の産業機器、組込機器に組み込まれ、流路を通過する流体の量を測定するための熱式のフローセンサである。ここで、流量センサ１は、本発明におけるサーモパイル型センサに相当する。 FIG. 1 is a schematic diagram showing an example of a sensor element 2 constituting the flow rate sensor 1 in this embodiment. The flow sensor 1 is incorporated in, for example, a gas meter, a combustion device, an internal combustion engine such as an automobile, a fuel cell, other industrial devices such as medical care, or an embedded device, and is a thermal type for measuring the amount of fluid passing through a flow path. It is a flow sensor. Here, the flow rate sensor 1 corresponds to the thermopile type sensor in the present invention.
　図１（ａ）は本実施例における流量センサ１を構成するセンサ素子２の斜視図、図１（ｂ）は図１（ａ）の断面Ｘ－Ｘに係る断面図である。センサ素子２は、ヒータ（加熱部）３と、ヒータ３を挟んで対称に設けられたサーモパイル（温度検出部）４とを備える。ヒータ３は、例えばポリシリコンで形成された抵抗である。サーモパイル４の形状は、平面視においてそれぞれ略矩形である。ヒータ３及びサーモパイル４は、絶縁薄膜５内に形成され、絶縁薄膜５はシリコン基板６上に設けられている。ここで、ヒータ３とサーモパイル４は、本発明におけるセンサ部に相当する。また、絶縁薄膜５、及びシリコン基板６はそれぞれ、本発明における薄膜部、及び基板に相当する。 1 (a) is a perspective view of the sensor element 2 constituting the flow rate sensor 1 in this embodiment, and FIG. 1 (b) is a cross-sectional view of the cross section XX of FIG. 1 (a). The sensor element 2 includes a heater (heating unit) 3 and a thermopile (temperature detection unit) 4 symmetrically provided with the heater 3 interposed therebetween. The heater 3 is, for example, a resistor made of polysilicon. The shape of the thermopile 4 is substantially rectangular in a plan view. The heater 3 and the thermopile 4 are formed in the insulating thin film 5, and the insulating thin film 5 is provided on the silicon substrate 6. Here, the heater 3 and the thermopile 4 correspond to the sensor unit in the present invention. Further, the insulating thin film 5 and the silicon substrate 6 correspond to the thin film portion and the substrate in the present invention, respectively.
　センサ素子２は、二つのサーモパイル４から出力された温度検出信号に基づいて、測定対象流体の流量を示す値を検出する。具体的には、センサ素子２は、一方のサーモパイル４から出力された温度検出信号ともう一方のサーモパイル４から出力された温度検出信号との差分を算出し、差分に基づいて測定対象流体の流量を示す値を求める。そして、センサ素子２は、流量を示す値を電子回路部（後述）に出力する。なお、図１（ａ）では二つのサーモパイル４を示しているが、サーモパイル４は二つ以上であればその数に限定はない。 The sensor element 2 detects a value indicating the flow rate of the fluid to be measured based on the temperature detection signals output from the two thermopile 4. Specifically, the sensor element 2 calculates the difference between the temperature detection signal output from one thermopile 4 and the temperature detection signal output from the other thermopile 4, and the flow rate of the fluid to be measured is based on the difference. Find the value that indicates. Then, the sensor element 2 outputs a value indicating the flow rate to the electronic circuit unit (described later). Although two thermopile 4s are shown in FIG. 1A, the number of thermopile 4s is not limited as long as they are two or more.
　図１（ａ）では簡略化して示しているが、サーモパイル４はそれぞれ、複数の熱電対７が絶縁薄膜５上に所定の間隔で並んで配置されることで構成されている。一対あたりの熱電対７は、ポリシリコン配線上に金属薄膜が形成された構成を有し、熱電対７の両端において、ポリシリコン配線が金属薄膜と接続されている。このうち、ヒータ３と同じ側で接続されている箇所が温接点８であり、ヒータ３と反対側で接続されている箇所が冷接点９である。すなわち、二つのサーモパイル４の間で、温接点８どうしは互いに比較的近い距離にあり、冷接点９どうしは互いに比較的遠い距離にある。 Although shown in a simplified manner in FIG. 1 (a), each thermopile 4 is configured by arranging a plurality of thermocouples 7 side by side on the insulating thin film 5 at predetermined intervals. The thermocouple 7 per pair has a structure in which a metal thin film is formed on the polysilicon wiring, and the polysilicon wiring is connected to the metal thin film at both ends of the thermocouple 7. Of these, the portion connected on the same side as the heater 3 is the hot contact 8, and the portion connected on the opposite side to the heater 3 is the cold contact 9. That is, between the two thermopile 4, the hot contacts 8 are relatively close to each other, and the cold contacts 9 are relatively far from each other.
　また、絶縁薄膜５上における、ヒータ３及びサーモパイル４の下方のシリコン基板６には、凹部であるキャビティエリア１０が設けられている。温接点８はキャビティエリア１０の上部に並んで位置し、冷接点９はシリコン基板６におけるキャビティエリア１０以外の領域に位置する。ヒータ３からの発熱は、キャビティエリア１０に放出されるため、シリコン基板６中への発熱の拡散は抑制される。よって、シリコン基板６におけるキャビティエリア１０以外の領域に位置する冷接点９の温度はほとんど上昇せず、ヒータ３の周囲に位置する温接点８との温度差がより生じやすい。温接点８と冷接点９との間に温度差が生じることで、起電力が効率的に得られる。 Further, the silicon substrate 6 below the heater 3 and the thermopile 4 on the insulating thin film 5 is provided with a cavity area 10 which is a recess. The hot contacts 8 are located side by side on the upper part of the cavity area 10, and the cold contacts 9 are located in regions other than the cavity area 10 in the silicon substrate 6. Since the heat generated from the heater 3 is discharged to the cavity area 10, the diffusion of the heat generated into the silicon substrate 6 is suppressed. Therefore, the temperature of the cold contact 9 located in the region other than the cavity area 10 of the silicon substrate 6 hardly rises, and the temperature difference from the hot contact 8 located around the heater 3 is more likely to occur. An electromotive force can be efficiently obtained by causing a temperature difference between the hot contact 8 and the cold contact 9.
　図２は、本実施例における流量センサ１を構成するセンサ素子２の仕組みを説明するための断面図である。図２は、点線の楕円によって、ヒータ３が発熱した場合の温度分布を模式的に示している。なお、ヒータ３近辺の温度分布ほど温度が高いものとする。図２（ａ）は、流体が流れていない状態でヒータ３に通電する場合の温度分布の一例を模式的に示している。一方、図２（ｂ）は、流体が点線の矢印の方向に流れている状態でヒータ３に通電する場合の温度分布の一例を模式的に示している。ヒータ３とサーモパイル４は、センサ素子２内において、点線の矢印の方向に沿って並んで配置されている。ヒータ３とサーモパイル４の各々の長手方向は、流体の流れ方向と直交する。 FIG. 2 is a cross-sectional view for explaining the mechanism of the sensor element 2 constituting the flow rate sensor 1 in this embodiment. FIG. 2 schematically shows the temperature distribution when the heater 3 generates heat by the dotted ellipse. It is assumed that the temperature distribution near the heater 3 is higher. FIG. 2A schematically shows an example of the temperature distribution when the heater 3 is energized in a state where no fluid is flowing. On the other hand, FIG. 2B schematically shows an example of the temperature distribution when the heater 3 is energized while the fluid is flowing in the direction of the dotted arrow. The heater 3 and the thermopile 4 are arranged side by side in the sensor element 2 along the direction of the dotted arrow. The longitudinal direction of each of the heater 3 and the thermopile 4 is orthogonal to the flow direction of the fluid.
　流体が流れていない場合、ヒータ３の熱は、ヒータ３を中心として対称に拡散する。よって、図２（ａ）の向きでヒータ３の左側の温接点８の温度とヒータ３の右側の温接点８の温度は同一となる。すなわち、サーモパイル４の出力電圧は生じない。一方、流体が流れている場合、ヒータ３の熱は、流体の流れの影響を受け、ヒータ３を中心として対称に拡散せず、流体の流れに沿って非対称に拡散していく。よって、図２（ｂ）の向きでヒータ３の左側の温接点８の温度とヒータ３の右側の温接点８の温度の間に差が生じる。そして、当該温度差に比例してサーモパイル４から出力電圧が生じる。また、流速に応じて温度差が大きくなるため、流速の大きさをサーモパイル４の起電力に基づいて検出できる。また、流体の流れる向きにより、図２（ｂ）に示す二つの温接点８の間の温度差の正負が逆転し、起電力の正負も逆転するため、流体の流れる向きを検出できる。センサ素子２は、このようなヒータ３の熱の分布の偏りを利用して、流量を示す値を出力する。 When no fluid is flowing, the heat of the heater 3 diffuses symmetrically around the heater 3. Therefore, in the direction of FIG. 2A, the temperature of the temperature contact 8 on the left side of the heater 3 and the temperature of the temperature contact 8 on the right side of the heater 3 are the same. That is, the output voltage of the thermopile 4 does not occur. On the other hand, when the fluid is flowing, the heat of the heater 3 is affected by the flow of the fluid and does not diffuse symmetrically around the heater 3, but diffuses asymmetrically along the flow of the fluid. Therefore, in the direction of FIG. 2B, there is a difference between the temperature of the temperature contact 8 on the left side of the heater 3 and the temperature of the temperature contact 8 on the right side of the heater 3. Then, an output voltage is generated from the thermopile 4 in proportion to the temperature difference. Further, since the temperature difference increases according to the flow velocity, the magnitude of the flow velocity can be detected based on the electromotive force of the thermopile 4. Further, depending on the flow direction of the fluid, the positive and negative of the temperature difference between the two temperature contacts 8 shown in FIG. 2 (b) are reversed, and the positive and negative of the electromotive force are also reversed, so that the flow direction of the fluid can be detected. The sensor element 2 outputs a value indicating a flow rate by utilizing such a bias in the heat distribution of the heater 3.
　センサ素子２の出力電圧ΔＶは、例えば次のような式（１）で表される。
Figure JPOXMLDOC01-appb-M000001
なお、Ｔｈはヒータ３の温度、Ｔａはサーモパイル４外側に設けられる周囲温度センサが測定した温度、Ｖｆは流速の平均値、Ａとｂは所定の定数である。 The output voltage ΔV of the sensor element 2 is expressed by, for example, the following equation (1).
Figure JPOXMLDOC01-appb-M000001
In addition, Th is the temperature of the heater 3, Ta is the temperature measured by the ambient temperature sensor provided on the outside of the thermopile 4, V f is the average value of the flow velocity, and A and b are predetermined constants.
　図３は、本実施例における流量センサ１の一例を示す斜視図である。流量センサ１は、センサ素子２と、回路を構成する電子回路部１１を同一チップ上に備えたモノリシック構造を有する。なお、図３ではセンサ素子２の一部の構造、すなわちヒータ３及びサーモパイル４の周辺の構造は簡略的に示す。また、サーモパイル４も簡略的に示す。絶縁薄膜５は、キャビティエリア１０の上面、及び電子回路部１１が形成されたシリコン基板６の上面を覆うように形成されている。図３に示す構造には金属保護膜１２が含まれており、図３において、点線Ｒと点線Ｓは金属保護膜１２の境目を表しており、点線Ｒと点線Ｓに囲まれた領域は金属保護膜１２によりカバーされている領域を表している。金属保護膜１２の熱伝導性により、流量センサ１の外部や電気回路部１１からの熱に対する均熱効果が得られる。なお、電子回路部１１は金属保護膜１２よりも下部に形成されており、チップの表面上では不可視であるため、図３では略矩形の点線で示す。 FIG. 3 is a perspective view showing an example of the flow rate sensor 1 in this embodiment. The flow rate sensor 1 has a monolithic structure in which the sensor element 2 and the electronic circuit unit 11 constituting the circuit are provided on the same chip. Note that FIG. 3 briefly shows a part of the structure of the sensor element 2, that is, the structure around the heater 3 and the thermopile 4. Moreover, the thermopile 4 is also shown briefly. The insulating thin film 5 is formed so as to cover the upper surface of the cavity area 10 and the upper surface of the silicon substrate 6 on which the electronic circuit portion 11 is formed. The structure shown in FIG. 3 includes a metal protective film 12. In FIG. 3, the dotted line R and the dotted line S represent the boundary between the metal protective film 12, and the region surrounded by the dotted line R and the dotted line S is a metal. It represents the area covered by the protective film 12. Due to the thermal conductivity of the metal protective film 12, a soaking effect on heat from the outside of the flow rate sensor 1 and the electric circuit portion 11 can be obtained. Since the electronic circuit portion 11 is formed below the metal protective film 12 and is invisible on the surface of the chip, it is shown by a substantially rectangular dotted line in FIG.
　流量センサ１のエッジから０μm以上４０μm以下の幅のエリアは、金属保護膜によりカバーされない。すなわち、図３のＷの値は少なくとも４０μmである。流量センサ１は製造工程において、チップ化する際にレーザーダイシングが適用されるが、金属保護膜１２によりカバーされている部分には上部からレーザーが入射できないため、金属保護膜１２によりカバーされないスペースを適度にとることが必要である。 The area with a width of 0 μm or more and 40 μm or less from the edge of the flow rate sensor 1 is not covered by the metal protective film. That is, the value of W in FIG. 3 is at least 40 μm. Laser dicing is applied to the flow sensor 1 when it is made into chips in the manufacturing process, but since the laser cannot be incident on the portion covered by the metal protective film 12 from above, a space not covered by the metal protective film 12 is created. It is necessary to take it moderately.
　また、図３に示す構造には金属端子１３ａ～１３ｅが含まれている。金属端子１３ａ～１３ｅは絶縁薄膜５側に開口を通じて外部に露出しており、外部端子への接続が可能である。金属端子１３ａ、１３ｂ、１３ｄ及び１３ｅは、電子回路部１１の入出力等のための端子であり、金属保護膜１２に接続されていない。なお、本実施例においては、電子回路部１２は、金属端子１３ａ～１３ｅの並びと、金属端子１３ａ～１３ｅの並びに近い側のサーモパイル４の間の金属保護膜１２の下部に形成されているが、それ以外の部分に形成されていても構わない。例えば、キャビティエリア１０の周辺における金属保護膜１２の下部の部分に形成されていてもよい。また、金属端子１３ａ、１３ｂ、１３ｄ及び１３ｅの周囲の領域は、金属保護膜１２によりカバーされていなくてもよい。 Further, the structure shown in FIG. 3 includes metal terminals 13a to 13e. The metal terminals 13a to 13e are exposed to the outside through an opening on the insulating thin film 5 side, and can be connected to the external terminal. The metal terminals 13a, 13b, 13d and 13e are terminals for input / output of the electronic circuit unit 11 and the like, and are not connected to the metal protective film 12. In this embodiment, the electronic circuit unit 12 is formed under the metal protective film 12 between the arrangement of the metal terminals 13a to 13e and the thermopile 4 on the near side of the metal terminals 13a to 13e. , It may be formed in other parts. For example, it may be formed in the lower portion of the metal protective film 12 around the cavity area 10. Further, the area around the metal terminals 13a, 13b, 13d and 13e may not be covered by the metal protective film 12.
　図４は、図３に示す流量センサ１の一例の概略構成を説明するための断面図である。図４（ａ）は図３の断面Ｙ－Ｙに係る断面図、図４（ｂ）は図３の断面Ｚ－Ｚに係る断面図である。なお、図４（ｂ）においては、電子回路部１１の下部のシリコン基板６は図示を省略し、また、シリコン基板６より上部を上下方向に拡大して図示している。図４（ａ）に示す通り、電子回路部１１と、冷接点９と、熱電対７において平面視でキャビティエリア１０と重なる部分の冷接点９側の一部の領域とが、金属保護膜１２によりカバーされている。電子回路部１１が、金属保護膜１２によりカバーされることで、電磁シールドの効果が得られ、電磁ノイズへの耐性が向上する。冷接点９が、金属保護膜１２によりカバーされることで、二対の熱電対７における冷接点９の間で温度差が生じにくくなり、流量の測定誤差が低減する。熱電対７において平面視でキャビティエリア１０と重なる部分の冷接点９側の一部の領域が、金属保護膜１２によりカバーされることで、キャビティエリア１０の寸法のバラツキが生じた場合においても、オフセット電圧が生じにくくなり、生産性が向上する。ここで、電子回路部１１は、本発明における回路部に相当する。 FIG. 4 is a cross-sectional view for explaining a schematic configuration of an example of the flow rate sensor 1 shown in FIG. 4 (a) is a cross-sectional view according to the cross section YY of FIG. 3, and FIG. 4 (b) is a cross-sectional view of the cross section ZZ of FIG. In FIG. 4B, the silicon substrate 6 at the lower part of the electronic circuit unit 11 is not shown, and the upper part of the silicon substrate 6 is enlarged in the vertical direction. As shown in FIG. 4A, the electronic circuit unit 11, the cold contact 9, and a part of the thermocouple 7 on the cold contact 9 side that overlaps the cavity area 10 in a plan view are formed by the metal protective film 12. Is covered by. By covering the electronic circuit portion 11 with the metal protective film 12, the effect of electromagnetic shielding is obtained, and the resistance to electromagnetic noise is improved. By covering the cold contact 9 with the metal protective film 12, a temperature difference between the cold contacts 9 in the two thermocouples 7 is less likely to occur, and a flow rate measurement error is reduced. Even if the dimensions of the cavity area 10 vary due to the metal protective film 12 covering a part of the thermocouple 7 on the cold contact 9 side that overlaps the cavity area 10 in a plan view. Offset voltage is less likely to occur, improving productivity. Here, the electronic circuit unit 11 corresponds to the circuit unit in the present invention.
　また、キャビティエリア１０の開口部の一方の端からもう一方の端までの距離、すなわち図４（ａ）のΦの値は１０００μmである。この場合、熱電対７が冷接点９側から温接点８側の方向に、キャビティエリア１０の開口部の端から金属保護膜１２によりカバーされる距離、すなわち図４（ａ）のＤの値は５μm以上１００μm以下である。ここで、図４（ａ）のＤの値が５μm未満である場合、キャビティエリア１０の寸法のバラツキが生じた際に、熱電対７において平面視でキャビティエリア１０と重なる部分を金属保護膜１２でカバーできない虞がある。また、流量センサ１の製造工程において、エッチングにより該範囲を５μm未満に収めることは困難である。また、図４（ａ）のＤの値が１００μm超過である場合、ヒータ３の熱が金属保護膜１２を伝達してシリコン基板６に逃げてしまうため、感度が低下してしまう虞がある。よって、本実施例のように、Ｄの値を５μm以上１００μm以下とすることで、流量センサ１の製造工程において、キャビティエリア１０の寸法のバラツキを厳密に管理する必要がなく、且つ、感度を保つことが可能であるので、生産性が向上する。 Further, the distance from one end of the opening of the cavity area 10 to the other end, that is, the value of Φ in FIG. 4A is 1000 μm. In this case, the distance at which the thermocouple 7 is covered by the metal protective film 12 from the end of the opening of the cavity area 10 in the direction from the cold contact 9 side to the warm contact 8 side, that is, the value D in FIG. 4A is It is 5 μm or more and 100 μm or less. Here, when the value of D in FIG. 4A is less than 5 μm, when the size of the cavity area 10 varies, the portion of the thermocouple 7 that overlaps with the cavity area 10 in a plan view is formed by the metal protective film 12. May not be covered by. Further, in the manufacturing process of the flow rate sensor 1, it is difficult to keep the range within 5 μm by etching. Further, when the value of D in FIG. 4A exceeds 100 μm, the heat of the heater 3 is transmitted through the metal protective film 12 and escapes to the silicon substrate 6, so that the sensitivity may decrease. Therefore, by setting the value of D to 5 μm or more and 100 μm or less as in this embodiment, it is not necessary to strictly control the dimensional variation of the cavity area 10 in the manufacturing process of the flow rate sensor 1, and the sensitivity can be improved. It is possible to keep it, so productivity is improved.
　また、金属保護膜１２の金属の主成分は、アルミニウムまたは金である。主成分がアルミニウムである場合、アルミニウムは金属の中でも比較的安価であるため、製造コストを抑えることが可能であり、且つ、アルミニウムは電子回路部１１を形成する際に一般的に用いられる金属であるため、金属保護膜１２の形成が容易になる。しかし、アルミニウムは金属の中でも比較的イオン化傾向が大きく、腐食しやすいため、金属保護膜１２の主成分として用いる際には、シリコン系の素材を含む表面保護層を表面に形成する必要がある。表面保護層は、金属端子１３ａ、１３ｂ、１３ｄ及び１３ｅを構成する金属膜上や金属端子１３における金属保護膜１２上は形成しない。主成分が金である場合、金は腐食耐性が高いため表面保護層の形成は不要である。この場合、金属保護膜１２の主成分に合わせて金属端子１３ａ、１３ｂ、１３ｄ及び１３ｅを構成する金属膜の主成分も金とする。 The main component of the metal of the metal protective film 12 is aluminum or gold. When the main component is aluminum, aluminum is relatively inexpensive among metals, so that the manufacturing cost can be suppressed, and aluminum is a metal generally used when forming the electronic circuit portion 11. Therefore, the metal protective film 12 can be easily formed. However, aluminum has a relatively high ionization tendency among metals and is easily corroded. Therefore, when used as the main component of the metal protective film 12, it is necessary to form a surface protective layer containing a silicon-based material on the surface. The surface protective layer is not formed on the metal film constituting the metal terminals 13a, 13b, 13d and 13e, or on the metal protective film 12 in the metal terminal 13. When the main component is gold, it is not necessary to form a surface protective layer because gold has high corrosion resistance. In this case, the main component of the metal film constituting the metal terminals 13a, 13b, 13d and 13e is also gold in accordance with the main component of the metal protective film 12.
　図４（ｂ）の断面図は、絶縁薄膜５及び電子回路部１１及び金属保護膜１２及び金属端子１３ａ～１３ｅの構成を示す。金属端子１３ａ～１３ｅは、絶縁薄膜５側の開口を通じて外部に露出している。金属端子１３ｃは、金属保護膜１２と電気的に接続されている。金属端子１３ａ、１３ｂ、１３ｄ及び１３ｅは、金属保護膜１２の下部に形成されている電子回路部１１の所定の信号線に電気的に接続されている。ここで、所定の信号線とは、入出力線、または電源及びグランドを含む。なお、金属保護膜１２の厚さＴは、金属端子１３ａ、１３ｂ、１３ｄ及び１３ｅを構成する金属膜の厚さＴ１～Ｔ４と等しい。 The cross-sectional view of FIG. 4B shows the configuration of the insulating thin film 5, the electronic circuit portion 11, the metal protective film 12, and the metal terminals 13a to 13e. The metal terminals 13a to 13e are exposed to the outside through the opening on the insulating thin film 5 side. The metal terminal 13c is electrically connected to the metal protective film 12. The metal terminals 13a, 13b, 13d and 13e are electrically connected to a predetermined signal line of the electronic circuit unit 11 formed in the lower part of the metal protective film 12. Here, the predetermined signal line includes an input / output line, a power supply, and a ground. The thickness T of the metal protective film 12 is equal to the thicknesses T1 to T4 of the metal films constituting the metal terminals 13a, 13b, 13d and 13e.
〔変形例１〕
　次に、本発明の変形例１について説明する。本変形例においては、実施例１に示した流量センサ１と構成が異なる流量センサについて説明する。 [Modification 1]
Next, a modification 1 of the present invention will be described. In this modification, a flow rate sensor having a configuration different from that of the flow rate sensor 1 shown in the first embodiment will be described.
　図５は、図３に示す流量センサ１の変形例を示す斜視図である。なお、図５ではセンサ素子２の一部の構造、すなわちヒータ３及びサーモパイル４の周辺の構造は簡略的に示す。また、サーモパイル４も簡略的に示す。図３と比較して、ヒータ３及びサーモパイル４及びキャビティエリア１０の配置角度が９０度異なる。モノリシック構造を有する点や、点線Ｒと点線Ｓに囲まれた領域が金属保護膜１２によりカバーされている点や、金属端子１３ａ～１３ｅが形成されている点は同様である。 FIG. 5 is a perspective view showing a modified example of the flow rate sensor 1 shown in FIG. Note that FIG. 5 briefly shows a part of the structure of the sensor element 2, that is, the structure around the heater 3 and the thermopile 4. Moreover, the thermopile 4 is also shown briefly. Compared with FIG. 3, the arrangement angles of the heater 3, the thermopile 4, and the cavity area 10 are different by 90 degrees. The points having a monolithic structure, the point that the region surrounded by the dotted line R and the dotted line S is covered by the metal protective film 12, and the point that the metal terminals 13a to 13e are formed are the same.
　図５に示す構成では、図３に示す構成と比較して、冷接点９が電子回路部１１から離れた位置に形成されているため、冷接点９が電子回路部１１の発熱の影響を受けにくく、二対のサーモパイル４における冷接点９の間で温度差が生じにくくなる。また、図５に示す構成では、図３に示す構成と比較して、ヒータ３とサーモパイル４の並びの方向が９０度回転し、流量を検知する方向がチップ１の短手方向となっている。これにより、計測対象の流体が、金属端子１３ａ～１３ｅに接続されるワイヤボンディングによる気流の乱れを受けづらくなり、流量の検知性が向上する。図５に示す構成は、実際に設計が可能である。 In the configuration shown in FIG. 5, since the cold contact 9 is formed at a position farther from the electronic circuit unit 11 as compared with the configuration shown in FIG. 3, the cold contact 9 is affected by the heat generated by the electronic circuit unit 11. It is difficult, and it is difficult for a temperature difference to occur between the cold contacts 9 in the two pairs of thermopile 4. Further, in the configuration shown in FIG. 5, the direction in which the heater 3 and the thermopile 4 are arranged is rotated by 90 degrees as compared with the configuration shown in FIG. 3, and the direction in which the flow rate is detected is the lateral direction of the chip 1. .. As a result, the fluid to be measured is less likely to receive turbulence of the air flow due to wire bonding connected to the metal terminals 13a to 13e, and the detectability of the flow rate is improved. The configuration shown in FIG. 5 can be actually designed.
〔実施例２〕
　次に、本発明の実施例２について説明する。実施例１では、サーモパイル型センサを流量センサ１に適用した例について説明したが、本実施例では、サーモパイル型センサを赤外線センサに適用した例について説明する。 [Example 2]
Next, Example 2 of the present invention will be described. In the first embodiment, an example in which the thermopile type sensor is applied to the flow rate sensor 1 has been described, but in this embodiment, an example in which the thermopile type sensor is applied to the infrared sensor will be described.
　図６は、本実施例における赤外線センサ１５の概略構成を説明するための断面図である。基本的な構成は流量センサ１と類似しているため、平面図は省略する。図４（ａ）の断面図と比較して、図６にはヒータ３が備わっていない。また、必要に応じて赤外線吸収膜もしくは赤外線吸収体を熱電対７の温接点８のエリアに付与されるが、図６では省略している。熱源として、図６の矢印の方向に外部から赤外線が照射され、熱電対７が温められる。外部からの照射により、赤外線が当たる範囲は広範囲であるが、シリコン基板６の大部分が金属保護膜１２によりカバーされ、赤外線の入射が防止されるため、シリコン基板６の温度上昇が抑制される。また、金属保護膜１２により冷接点９はカバーされているが、温接点８はカバーされていないため、赤外線の照射により温接点８と冷接点９の間により大きな温度差を生じさせることが可能である。 FIG. 6 is a cross-sectional view for explaining a schematic configuration of the infrared sensor 15 in this embodiment. Since the basic configuration is similar to the flow rate sensor 1, the plan view is omitted. Compared to the cross-sectional view of FIG. 4 (a), FIG. 6 does not include the heater 3. Further, if necessary, an infrared absorber film or an infrared absorber is applied to the area of the hot contact 8 of the thermocouple 7, but it is omitted in FIG. As a heat source, infrared rays are irradiated from the outside in the direction of the arrow in FIG. 6, and the thermocouple 7 is heated. Although the range exposed to infrared rays is wide due to external irradiation, most of the silicon substrate 6 is covered by the metal protective film 12 to prevent infrared rays from being incident on the silicon substrate 6, so that the temperature rise of the silicon substrate 6 is suppressed. .. Further, since the cold contact 9 is covered by the metal protective film 12, but the warm contact 8 is not covered, it is possible to generate a larger temperature difference between the hot contact 8 and the cold contact 9 by irradiating infrared rays. Is.
　また、図６（ａ）に示すように、本実施例の赤外線センサ１５では、電子回路部１１と冷接点９の間の、シリコン基板６上に温度センサ１４が備わっている。温度センサ１４は周囲温度を測定することが可能である。ここで周囲温度とは、温度センサ１４の付近の冷接点９の温度のことを表す。赤外線の照射によって生じる温接点８と冷接点９の間の温度差ΔＴと、周囲温度Ｔａｔｍを測定することで、対象物の温度Ｔは、例えば次のような式（２）で表される。
Figure JPOXMLDOC01-appb-M000002
本実施形態における赤外線センサ１５を用いることで、ΔＴに加えてＴａｔｍの測定も可能であるため、Ｔを直接算出することが可能である。 Further, as shown in FIG. 6A, in the infrared sensor 15 of this embodiment, the temperature sensor 14 is provided on the silicon substrate 6 between the electronic circuit unit 11 and the cold contact 9. The temperature sensor 14 can measure the ambient temperature. Here, the ambient temperature represents the temperature of the cold contact 9 in the vicinity of the temperature sensor 14. By measuring the temperature difference ΔT between the hot contact 8 and the cold contact 9 caused by the irradiation of infrared rays and the ambient temperature Tatm , the temperature T of the object is expressed by the following equation (2), for example. ..
Figure JPOXMLDOC01-appb-M000002
By using the infrared sensor 15 in this embodiment, it is possible to measure T atm in addition to ΔT, so that T can be calculated directly.
　また、温度センサ１４が備わっている場合、金属保護膜１２によりカバーされることで、冷接点９と温度センサ１４の間の熱伝導性が良好となり、これらの周辺の温度が均一化し、Ｔの算出値の誤差を低減することが可能である。また、温度センサ１４は金属保護膜１２によりカバーされているため、赤外線の照射によって温度センサ１４が温められることを防止することが可能である。なお、温度センサ１４は、電子回路の一部として機能するため、電子回路部１１を構成する部分として電子回路部１１に内蔵されていてもよい。 Further, when the temperature sensor 14 is provided, the heat conductivity between the cold contact 9 and the temperature sensor 14 is improved by being covered with the metal protective film 12, the temperature around these is made uniform, and the temperature of T is increased. It is possible to reduce the error of the calculated value. Further, since the temperature sensor 14 is covered with the metal protective film 12, it is possible to prevent the temperature sensor 14 from being heated by irradiation with infrared rays. Since the temperature sensor 14 functions as a part of the electronic circuit, it may be built in the electronic circuit unit 11 as a portion constituting the electronic circuit unit 11.
　また、図６（ｂ）に示すように、電子回路部１１がシリコン基板６上に形成されておらず、シリコン基板６のエリア外に形成されていてもよい。この構成においては、温度センサ１４のみが、金属保護膜１２によりカバーされることになる。この場合には、温度センサ１４が回路部に相当するということが可能である。 Further, as shown in FIG. 6B, the electronic circuit unit 11 may not be formed on the silicon substrate 6 but may be formed outside the area of the silicon substrate 6. In this configuration, only the temperature sensor 14 will be covered by the metal protective film 12. In this case, it is possible that the temperature sensor 14 corresponds to the circuit unit.
　なお、本実施例においては、温度センサ１４には、抵抗変化式、ダイオード式、サーミスタ等の種類がある。また、本実施例においては、温度センサ１４を赤外線センサ１５に適用した例を示したが、温度センサ１４を流量センサ１に適用してもよい。 In this embodiment, the temperature sensor 14 includes types such as a resistance change type, a diode type, and a thermistor. Further, in this embodiment, an example in which the temperature sensor 14 is applied to the infrared sensor 15 is shown, but the temperature sensor 14 may be applied to the flow rate sensor 1.
　　なお、以下には本発明の構成要件と実施例の構成とを対比可能とするために、本発明の構成要件を図面の符号付きで記載しておく。
＜発明１＞
　基板（６）上の所定面側に開口した凹部であるキャビティエリア（１０）と、
　前記キャビティエリアの開口を覆うように形成された薄膜部（５）と、
　前記薄膜部に形成され、温度の検出に係るセンサ部（４）と、
　前記基板上の所定面に形成され、電気回路を構成する回路部（１１）と、を備え、
　前記センサ部は、前記薄膜部に所定の間隔で並列して配置される複数の熱電対（７）から成り、並んで配置される二つ以上のサーモパイル（４）を有し、
　前記熱電対の各々は、隣のサーモパイルに近い側の端部に形成された温接点（８）、及び前記隣のサーモパイルに遠い側の端部に形成された冷接点（９）を有し、前記温接点は前記キャビティエリア上に位置し、前記冷接点は前記基板における前記キャビティエリア以外の領域上に位置し、
　前記回路部と、前記冷接点と、前記サーモパイルにおいて平面視で前記キャビティエリアと重なる部分の前記冷接点側の一部の領域とが、金属保護膜（１２）によりカバーされていることを特徴とする、
　サーモパイル型センサ（１）。 In addition, in order to make it possible to compare the constituent elements of the present invention with the configurations of the examples, the constituent elements of the present invention are described below with reference numerals in the drawings.
<Invention 1>
Cavity area (10), which is a recess opened on the predetermined surface side on the substrate (6), and
A thin film portion (5) formed so as to cover the opening of the cavity area,
A sensor unit (4) formed in the thin film portion and related to temperature detection, and
A circuit unit (11) formed on a predetermined surface on the substrate and constituting an electric circuit is provided.
The sensor unit comprises a plurality of thermocouples (7) arranged in parallel at predetermined intervals in the thin film unit, and has two or more thermopile (4) arranged side by side.
Each of the thermocouples has a warm contact (8) formed at the end near the adjacent thermopile and a cold contact (9) formed at the end far from the adjacent thermopile. The thermocouple is located on the cavity area and the cold junction is located on a region of the substrate other than the cavity area.
The circuit portion, the cold contact, and a part of the region of the thermopile on the cold contact side that overlaps the cavity area in a plan view are covered with a metal protective film (12). do,
Thermopile type sensor (1).
１　　　　　　：流量センサ
２　　　　　　：センサ素子
３　　　　　　：ヒータ
４　　　　　　：サーモパイル
５　　　　　　：絶縁薄膜
６　　　　　　：シリコン基板
７　　　　　　：熱電対
８　　　　　　：温接点
９　　　　　　：冷接点
１０　　　　　：キャビティエリア
１１　　　　　：電子回路部
１２　　　　　：金属保護膜
１３ａ―１３ｅ：金属端子
１４　　　　　：温度センサ
１５　　　　　：赤外線センサ 1: Flow sensor 2: Sensor element 3: Heater 4: Thermopile 5: Insulating thin film 6: Silicon substrate 7: Thermocouple 8: Warm contact 9: Cold contact 10: Cavity area 11: Electronic circuit unit 12: Metal protective film 13a- 13e: Metal terminal 14: Temperature sensor 15: Infrared sensor

Claims (8)

  1. 　基板上の所定面側に開口した凹部であるキャビティエリアと、
    　前記キャビティエリアの開口を覆うように形成された薄膜部と、
    　前記薄膜部に形成され、温度の検出に係るセンサ部と、
    　前記基板上の所定面に形成され、電気回路を構成する回路部と、を備え、
    　前記センサ部は、前記薄膜部に所定の間隔で並列して配置される複数の熱電対から成り、並んで配置される二つ以上のサーモパイルを有し、
    　前記熱電対の各々は、隣のサーモパイルに近い側の端部に形成された温接点、及び前記隣のサーモパイルに遠い側の端部に形成された冷接点を有し、前記温接点は前記キャビティエリア上に位置し、前記冷接点は前記基板における前記キャビティエリア以外の領域上に位置し、
    　前記回路部と、前記冷接点と、前記サーモパイルにおいて平面視で前記キャビティエリアと重なる部分の前記冷接点側の一部の領域とが、金属保護膜によりカバーされていることを特徴とする、
    　サーモパイル型センサ。     A cavity area, which is a recess on the substrate that opens on the predetermined surface side,
    A thin film portion formed so as to cover the opening of the cavity area,
    A sensor unit formed on the thin film portion and related to temperature detection, and a sensor portion.
    A circuit unit formed on a predetermined surface on the substrate and constituting an electric circuit is provided.
    The sensor unit is composed of a plurality of thermocouples arranged in parallel at predetermined intervals in the thin film unit, and has two or more thermopile arranged side by side.
    Each of the thermocouples has a warm contact formed at the end closer to the adjacent thermopile and a cold contact formed at the end farther from the adjacent thermopile, the warm contact being the cavity. Located on the area, the cold junction is located on a region of the substrate other than the cavity area.
    The circuit portion, the cold contact, and a part of the region of the thermopile on the cold contact side that overlaps the cavity area in a plan view are covered with a metal protective film.
    Thermopile type sensor.
  2. 　前記金属保護膜は、前記回路部におけるグランドに接続されていることを特徴とする、
    　請求項１に記載のサーモパイル型センサ。     The metal protective film is connected to a ground in the circuit portion.
    The thermopile type sensor according to claim 1.
  3. 　前記基板上には、複数の金属端子が形成されており、
    　前記複数の金属端子は、前記薄膜部側の開口を通じて外部に露出しており、
    　前記複数の金属端子のうち、一部の金属端子は、前記金属保護膜に接続され、
    　前記複数の金属端子のうち、上記一部の金属端子以外の金属端子は、金属膜により形成され前記回路部の所定の信号線に接続されており、
    　前記金属膜は、前記金属保護膜と、同じ厚さであることを特徴とする、
    　請求項１または２に記載のサーモパイル型センサ。     A plurality of metal terminals are formed on the substrate.
    The plurality of metal terminals are exposed to the outside through the opening on the thin film portion side.
    Of the plurality of metal terminals, some of the metal terminals are connected to the metal protective film, and the metal terminals are connected to the metal protective film.
    Of the plurality of metal terminals, the metal terminals other than some of the metal terminals are formed of a metal film and are connected to a predetermined signal line of the circuit portion.
    The metal film is characterized by having the same thickness as the metal protective film.
    The thermopile type sensor according to claim 1 or 2.
  4. 　前記基板の外周から４０μm以下の幅のエリアは、前記金属保護膜によりカバーされないことを特徴とする、
    　請求項１から３のいずれか一項に記載のサーモパイル型センサ。     An area having a width of 40 μm or less from the outer periphery of the substrate is not covered by the metal protective film.
    The thermopile type sensor according to any one of claims 1 to 3.
  5. 　前記一部の領域の前記温接点側の端部における、前記キャビティエリアの開口部の端からの距離は、５μm以上１００μm以下であることを特徴とする、
    　請求項１から４のいずれか一項に記載のサーモパイル型センサ。     The distance from the end of the opening of the cavity area at the end of the partial region on the warm contact side is 5 μm or more and 100 μm or less.
    The thermopile type sensor according to any one of claims 1 to 4.
  6. 　前記金属保護膜の主成分は、アルミニウムであり、
    　前記金属保護膜の表面には、シリコン系の材質を含む表面保護層が形成されており、
    　前記表面保護層は、前記複数の金属端子上には形成されないことを特徴とする、
    　請求項１から５のいずれか一項に記載のサーモパイル型センサ。     The main component of the metal protective film is aluminum.
    A surface protective layer containing a silicon-based material is formed on the surface of the metal protective film.
    The surface protective layer is not formed on the plurality of metal terminals.
    The thermopile type sensor according to any one of claims 1 to 5.
  7. 　前記金属保護膜の主成分は、金であることを特徴とする、
    　請求項１から５のいずれか一項に記載のサーモパイル型センサ。     The main component of the metal protective film is gold.
    The thermopile type sensor according to any one of claims 1 to 5.
  8. 　前記基板上に温度センサを備え、
    　前記温度センサは、前記金属保護膜によりカバーされていることを特徴とする、
    　請求項１に記載のサーモパイル型センサ。     A temperature sensor is provided on the substrate.
    The temperature sensor is covered by the metal protective film.
    The thermopile type sensor according to claim 1.
PCT/JP2021/007659 2020-08-07 2021-03-01 Thermopile sensor WO2022030039A1 (en)

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US11953357B2 (en) 2021-03-11 2024-04-09 MMI Semiconductor Co., Ltd. Flow sensor chip

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