JP2022030781A - Thermopile type sensor - Google Patents

Abstract

To provide a thermopile type sensor that obtains, through formation of a metal protective film, an improvement in resistance against electromagnetic noise, a reduction of error in measurement of the flow rate of fluid, and an improvement in productivity as effects.SOLUTION: A thermopile type sensor comprises a substrate, a cavity area, a thin film part, a sensor part, and a circuit part. The sensor part includes a thermopile consisting of a plurality of thermocouples each having a hot junction and a cold junction. The circuit part, cold junctions, and a partial area on the cold junction side of a portion overlapping the cavity area in plan view in the thermopile are covered by a metal protective film.SELECTED DRAWING: Figure 4

Description

The present invention relates to a thermopile type sensor.

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).

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).

Japanese Patent No. 5112728 European Patent Application Publication No. 1092962 European Patent Application Publication No. 2930475 Japanese Patent No. 5861497

Zhou, Huchuan, et al. "Development of a thermopile infrared sensor using stacked double mountains silicon layers based on the CMOS process." Journal of Micromechanics and Microengineering 23.6 (2013): 065026.

In the thermopile type sensor as described above, high sensitivity is generally required 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.

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.

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. 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.

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, respectively, 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.

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.

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.

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.

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.

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.

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.

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.

In the present invention, the means for solving the above-mentioned problems can be used in combination as much as possible.

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.

It is a schematic diagram which shows an example of the sensor element which constitutes the flow rate sensor in an Example. It is sectional drawing for demonstrating the mechanism of the sensor element constituting the flow rate sensor in an Example. It is a perspective view which shows an example of the flow rate sensor in an Example. It is sectional drawing for demonstrating the schematic structure of the example of the flow rate sensor shown in FIG. It is a perspective view which shows the modification of the flow rate sensor shown in FIG. It is sectional drawing for demonstrating the schematic structure of the infrared sensor in an Example.

[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.

In a thermocouple, when the hot contact senses the heat of the heater, an electromotive force is generated by 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.

The thermopile is provided symmetrically with the heater in between, and the side where the fluid flows along the flow path at the time of flow rate detection 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 portion 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.

However, in the above thermopile type sensor, the circuit part is exposed to the 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.

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.

[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.

<Device 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. Here, the flow rate sensor 1 corresponds to the thermopile type sensor in the present invention.

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 relating to 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.

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.

Although shown in a simplified manner in FIG. 1 (a), each thermopile 4 is configured such that a plurality of thermocouples 7 are arranged 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.

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 in 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. 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.

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 contact 8 on the right side of the heater 3
The temperature of is 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, 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 in the direction of FIG. 2B. 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.

・・・（１）
なお、Ｔ_ｈはヒータ３の温度、Ｔ_ａ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、Ｖ_ｆ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).

... (1)
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.

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.

The area having 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.

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.

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.

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, the cavity area 10 is used in the manufacturing process of the flow rate sensor 1.
It is not necessary to strictly control the variation in the dimensions of the product, and the sensitivity can be maintained, so that the productivity is improved.

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.

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.

[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.

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 where the region surrounded by the dotted line R and the dotted line S is covered by the metal protective film 12, and the point where the metal terminals 13a to 13e are formed are the same.

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.

[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. 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.

・・・（２）
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Ｔ_ａｔｍ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, for example, the following equation (2). ..

... (2)
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.

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.

Further, as shown in FIG. 6B, the electronic circuit portion 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.

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.

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: 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)

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. The metal protective film is connected to a ground in the circuit portion.
The thermopile type sensor according to claim 1. 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. 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. 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. 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. The main component of the metal protective film is gold.
The thermopile type sensor according to any one of claims 1 to 5. 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.

Images