JP2007322320A - Flow sensor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow sensor capable of sufficiently correcting temperature even if there is a difference between fluid temperature and ambient temperature. <P>SOLUTION: A flow sensor comprises a pair of temperature sensors 14, 15 positioned at the upper stream P and the lower stream Q in the flow direction of fluid on the surface of a silicone substrate 11; a microheater 13 positioned between a pair of the temperature sensors 14, 15 on the surface of the silicone substrate 11; and a reference resistance 16 for measuring an ambient temperature provided on the silicone substrate 11 so as not to directly contact with the fluid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a flow sensor used for measuring the flow rate of a fluid such as gas or water flowing in a flow path, and a method for manufacturing the same.

  2. Description of the Related Art Conventionally, as a flow rate measuring device for measuring the flow rate of a fluid such as gas or water flowing in a flow path, a device using a thermal type flow sensor is known (see, for example, Patent Document 1).

  In this thermal type flow sensor, a heater having a temperature higher than the temperature of the fluid is installed in the flow of the fluid whose flow is to be measured, and the temperature distribution of the fluid heated by the heater changes as the flow velocity increases. It uses the principle of doing.

  6 (A) and 6 (B) show an example of a conventional thermal type flow sensor, FIG. 6 (A) is a plan view of the conventional flow sensor, and FIG. 6 (B) is a cross-sectional view of the conventional flow sensor. It is.

  6 (A) and 6 (B), the flow sensor 100 forms a concave void portion 102a on one surface of a silicon substrate 102, and an insulating thin film 103 is formed on one surface of the silicon substrate 102 so as to cover the void portion 102a. A thin film diaphragm 103 a is formed on the gap 102 a by a part of the insulating thin film 103. The diaphragm 103a is thermally insulated from the silicon substrate 102 by a space (air) in the gap 102a.

A heater 104 is provided at the center of the surface of the diaphragm 103a. Further, temperature measuring bodies 105 and 106 are provided at symmetrical positions with respect to the heater 104, respectively. Further, a resistor 107 for measuring ambient temperature is provided on the surface of the insulating thin film 103 outside the diaphragm 103a. The silicon substrate 102 is covered with a protective film 108 so as to cover the heater 104, the temperature measuring elements 105 and 106, and the resistor 107. In FIG. 6A, reference numerals 104a and 104b, reference numerals 105a and 105b, reference numerals 106a and 106b, and reference numerals 107a and 107b are power supply terminals and output terminals, respectively.
Japanese Patent Laid-Open No. 2002-202168

  By the way, in the flow sensor 100 of the flow rate measuring apparatus configured as described above, the resistor 107 for measuring the ambient temperature is provided on the same silicon substrate 102 as the temperature measuring bodies 105 and 106. Accordingly, the temperature measuring bodies 105 and 106 functioning as temperature detecting elements of the silicon substrate 102 and the resistor 107 as the temperature detecting element for measuring the ambient temperature are arranged in the same flow path, and the fluid temperature and When the ambient temperature is completely different, there has been a problem that the temperature correction is not sufficiently performed.

  Therefore, in view of the problems described above, an object of the present invention is to provide a flow sensor capable of performing sufficient temperature correction even when the fluid temperature and the ambient temperature are different, and a manufacturing method thereof.

  The flow rate measuring device according to claim 1, which has been made in accordance with the present invention to solve the above-described problems, is a pair of temperature sensors provided on the surface side of the base body and positioned upstream and downstream in the fluid passage direction, and the base body A heater located between the pair of temperature sensors and a temperature sensor for measuring the ambient temperature provided on the back side of the base so as not to directly contact the fluid. Features.

  According to a second aspect of the present invention, in the flow sensor according to the first aspect, the temperature sensor for measuring the ambient temperature is provided on the back surface side of the substrate.

  According to a third aspect of the present invention, in the flow sensor according to the first aspect of the present invention, the flow sensor according to the first aspect includes an insulating film that covers a surface of the base body, and the temperature sensor for measuring the ambient temperature includes the base body and the insulating film. It is provided so as to be interposed between them.

  The method of manufacturing a flow rate measuring device according to claim 4, which is made according to the present invention to solve the above-described problem, includes a pair of temperature sensors on the surface side of the base and a heater so as to be positioned between the pair of temperature sensors. A conductive line forming step to be formed; and an ambient temperature sensor forming step to form a temperature sensor for measuring the ambient temperature on the substrate so as not to directly contact the fluid.

  As described above, according to the flow sensor of the present invention described in claim 1, the temperature of the ambient temperature (sensor chip or the like) can be accurately detected regardless of the temperature of the fluid flowing in the flow path. A highly accurate flow rate can be detected, and sufficient temperature correction can be performed. Therefore, even if the fluid temperature and the ambient temperature are different, sufficient temperature correction can be performed, which can contribute to improvement in accuracy of flow rate measurement using the flow sensor.

  According to the second aspect of the present invention, in addition to the effect of the first aspect of the invention, a temperature sensor for measuring the ambient temperature is provided on the back side of the base. Since a temperature sensor for measuring the ambient temperature can be provided between the substrate and the substrate, only the ambient temperature can be reliably detected without being affected by the fluid temperature.

  According to the invention described in claim 3, in addition to the effect of the invention described in claim 1, a temperature sensor for measuring the ambient temperature is interposed between the base and the insulating film covering the surface of the base. As a result, manufacturing efficiency can be improved, and only the ambient temperature can be reliably detected.

  As described above, according to the method for manufacturing a flow rate measuring device of the present invention described in claim 4, the pair of temperature sensors and the heaters are formed on the surface side of the base so as to be positioned between the pair of temperature sensors. Since the temperature sensor for measuring the ambient temperature is formed on the back side of the base so as not to come into direct contact with the fluid, the ambient temperature (sensor chip, etc.) can be accurately measured regardless of the temperature of the fluid flowing in the flow path. Therefore, the flow rate can be detected with higher accuracy, and sufficient temperature correction can be performed. Therefore, even if the fluid temperature and the ambient temperature are different, sufficient temperature correction can be performed, which can contribute to improvement in accuracy of flow rate measurement using the flow sensor.

  Next, a flow measurement device using a flow sensor according to an embodiment of the present invention will be described below with reference to the drawings. 1A is a conceptual diagram of a flow rate measuring device according to one embodiment of the present invention, FIG. 1B is a schematic cross-sectional view of a flow sensor used in the flow rate measuring device according to one embodiment of the present invention, FIG. 2 is a plan view of a flow sensor used in the flow rate measuring apparatus according to the embodiment of the present invention.

  As shown in FIGS. 1A and 1B, the flow rate measuring device includes a flow sensor 10 disposed in a flow path R that conveys a fluid such as gas or water, and power supply to the flow sensor 10. And a control unit 30 that performs temperature signal control and the like.

  The flow sensor 10 includes a silicon substrate (base body) 11, an insulating thin film 12 provided on the surface side of the silicon substrate 11, that is, a surface side in direct contact with the flow path R, and a diaphragm 12 a formed on a part thereof, and a diaphragm 12 a. The heater 13 made of platinum (Pt), permalloy (iron), nickel (Ni), etc. formed on the upper side, and the upstream side as a temperature sensor formed on the upstream side P in the fluid conveyance direction of the flow path R from the heater 13 The thermopile 14, the downstream thermopile 15 as a temperature sensor formed on the downstream Q side in the fluid conveyance direction of the flow path R from the heater 13, and the back side of the silicon substrate 11, that is, the surface side not directly in contact with the flow path R And a reference resistor (or a temperature measuring diode) 16 as a temperature sensor for measuring ambient temperature.

  As shown in FIG. 2, the heater 13 includes power terminals 13 </ b> A and 13 </ b> B and power terminals 13 </ b> C and 13 </ b> D that supply a drive current whose current is controlled by the control unit 30 from a power supply (not shown).

  The upstream thermopile 14 and the downstream thermopile 15 include output terminals 14A and 14B and output terminals 15A and 15B for outputting temperature signals to the control unit 30, respectively.

  The reference resistor 16 includes output terminals 16A and 16B for outputting an ambient temperature signal to the control unit 30.

  In such a configuration, the flow sensor 10 is disposed in a substantially orthogonal direction with respect to the heater 13 in the fluid conveyance direction (from the upstream P side to the downstream Q side), and detects physical property state information of the fluid. At this time, the reference resistor 16 can output the temperature of the silicon substrate 13 as the ambient temperature to the control unit 30 without being affected by the temperature increase accompanying the heat generation of the heater 13.

  The control unit 30 controls the heating of the heater 13 so as to rise above a certain temperature from the ambient temperature.

  When the heater 13 starts heating, the heat generated from the heater 13 is a synergy between the thermal diffusion effect of the fluid and the flow velocity of the fluid flowing from the upstream P side toward the downstream Q side using the fluid flowing through the flow path R as a medium. The effect is transmitted to each thermopile 14,15.

  That is, when there is no flow velocity, the heat is diffused evenly to the upstream thermopile 14 and the downstream thermopile 15, and the upstream temperature signal from the upstream thermopile 14 and the downstream temperature signal from the downstream thermopile 15 are transmitted. The temperature difference signal becomes zero.

  On the other hand, when a flow rate is generated in the fluid, the amount of heat transferred to the downstream thermopile 15 is increased by the flow rate, and the amount of heat transferred to the upstream thermopile 14 is decreased. The temperature difference signal has a value corresponding to the flow velocity.

  The control unit 30 corrects the difference signal between the upstream temperature signal and the downstream temperature signal input from the upstream thermopile 14 and the downstream thermopile 15 based on the ambient temperature signal input from the reference resistor 16, Based on the difference signal, the flow velocity of the fluid is measured.

  According to the flow sensor 10 described above, it is possible to accurately detect the temperature of the ambient temperature (sensor chip or the like) regardless of the temperature of the fluid flowing in the flow path R, and thus it is possible to detect a more accurate flow rate. And sufficient temperature correction can be performed. Therefore, even if the fluid temperature and the ambient temperature are different, sufficient temperature correction can be performed, which can contribute to improvement in accuracy of flow rate measurement using the flow sensor 10.

  Next, an example of a manufacturing method of such a flow sensor 10 will be described based on the drawings of FIGS.

  3 and 4 show an example of the manufacturing method of the flow sensor 10 of the present invention, and FIGS. 3A to 3H are explanatory views showing the manufacturing process of the flow sensor 10 in time series. 4A is a perspective view of the main part in the course of the manufacturing process of the flow sensor, and FIG. 4B is an enlarged sectional view of the main part.

  The flow sensor 10 includes a conductive thin film 17 made of a conductor such as high-concentration p-type silicon (p ++-Si) on the surface side of a silicon substrate 11 (see FIG. 3A) formed in a predetermined shape and size. After forming 18, an insulating film 12 is formed so as to cover the conductive thin films 17 and 18. In addition, an insulating film 19 is formed on the back surface of the silicon substrate 11 (see FIG. 3B).

  Next, the contact hole 20 is formed at a predetermined position of the insulating thin film 12 so that the output terminals 14A and 14B and the output terminals 15A and 15B of the thermopile 14 and 15 and the conductive thin films 17 and 18 are electrically connected to the insulating film 12. . Further, the center of the insulating film 19 is etched (see FIG. 3C).

  Furthermore, a heater 13, an upstream thermopile 14, and a downstream thermopile 15 are formed on the surface of the insulating film 12 using, for example, platinum or the like (see FIG. 3D), and correspond to the etched insulating film 19 portion. The silicon substrate 11 is etched to form a diaphragm 12a on the insulating film 12 (see FIG. 3E).

  Further, in this embodiment, the insulating film 40 shown in FIG. 4 is formed on the surface of the silicon substrate 11 subjected to the etching process, but the step and the insulating film 40 are omitted in FIG. If the insulating film 40 is unnecessary, it is not necessary to form it on the surface of the silicon substrate 11.

  Next, the reference resistor 16 is formed on the surface of the insulating film 19 (the back surface of the silicon substrate 11) (see FIG. 3F). At this time, as shown in FIG. 4, the output terminals 16A and 16B of the reference resistor 16 are formed from the silicon substrate 11 (the surface of the insulating film 40) to the diaphragm 12a and insulated through the contact holes 16C and the like. It is electrically connected to a conductive film 21 provided on the surface side of the film 12.

  Furthermore, the back surface side of the silicon substrate 11 is fixed to the stem 23 via an insulating adhesive 22 provided so as to cover the insulating film 19 including the reference resistor 16 (see FIG. 3G). The heater 13, the upstream thermopile 14, the downstream thermopile 15, and the reference resistor 16 are connected by wires 25, 26, and 27 via a pin 24 whose one end is fixed to the stem 23 (FIG. 3 ( H)).

  As described above, according to the manufacturing method of the flow sensor 10 of the first embodiment, the conductive thin films 17 and 18 are formed on the surface side of the silicon substrate 11 formed in a predetermined shape, and then the conductive thin films 17 and 18 are covered so as to cover the conductive thin films 17 and 18. A front surface side thin film forming step for forming the film 19, a back surface thin film forming step for forming an insulating film on the back surface of the silicon substrate 11, a pair of thermopiles 14 and 15 (temperature sensor) on the front surface side of the silicon substrate 11, and Conductive line forming steps for forming the heaters 13 so as to be positioned between the pair of thermopiles 14 and 15, respectively, and removing the back surface side of the silicon substrate 11 to provide a diaphragm 12a on the back surface of the insulating film 19 on the front surface side. A diaphragm forming step to be formed, and a reference resistor 16 (temperature) for measuring ambient temperature on the back side of the silicon substrate 11 And a ambient temperature sensor forming step of forming a capacitors).

  In the first embodiment described above, the manufacturing method of the flow sensor 10 in which the reference resistor 16 is formed on the back side of the silicon substrate 11 has been described. However, the reference resistor 16 described above is interposed between the silicon substrate 11 and the insulating film 12. A method for manufacturing the flow sensor 10 will be described.

  The flow sensor 10 includes a silicon substrate (base) 11, an insulating thin film 12 on which a diaphragm 12 a is formed, a heater 13, an upstream thermopile 14, a downstream thermopile 15, as in the first embodiment. A reference resistor 16 is provided as a temperature sensor for measuring the ambient temperature.

  The flow sensor 10 has the same basic configuration as that of the first embodiment except for the configuration of the reference resistor 16. The reference resistor 16 is provided so as to be interposed between the silicon substrate 11 and the insulating film 12.

  FIG. 5 shows an example of the manufacturing method of the flow sensor 10 of the present invention, and FIGS. 5A to 5G are explanatory diagrams showing the manufacturing process of the flow sensor 10 in time series.

  The flow sensor 10 first forms a reference resistor 16 on the surface side of a silicon substrate 11 (see FIG. 5A) formed in a predetermined shape and size, and at the same time uses high-concentration p-type silicon (p ++-Si) or the like. After the conductive thin films 17 and 18 made of a conductor are formed, the insulating film 12 is formed so as to cover the conductive thin films 17 and 18. In addition, an insulating film 19 is formed on the back surface of the silicon substrate 11 (see FIG. 5B).

  Next, the contact hole 20 is formed at a predetermined position of the insulating thin film 12 so that the output terminals 14A and 14B and the output terminals 15A and 15B of the thermopile 14 and 15 and the conductive thin films 17 and 18 are electrically connected to the insulating film 12. . Further, the center of the insulating film 19 is etched (see FIG. 5C).

  Furthermore, a heater 13, an upstream thermopile 14, and a downstream thermopile 15 are formed on the surface of the insulating film 12 using, for example, platinum or the like (see FIG. 5D), and correspond to the etched insulating film 19 portion. The silicon substrate 11 is etched to form a diaphragm 12a on the insulating film 12 (see FIG. 5E).

  Next, the back surface of the silicon substrate 11 is fixed to the stem 23 via an insulating adhesive 22 provided so as to cover the insulating film 19 including the reference resistor 16 (see FIG. 5F). The heater 13, the upstream thermopile 14, the downstream thermopile 15, and the reference resistor 16 are connected to each other by wires 25, 26, and 27 through a pin 24 whose one end is fixed to the stem 23 (FIG. 5). (See (G)).

  As described above, according to the manufacturing method of the flow sensor 10 of the second embodiment, the ambient temperature sensor forming step of forming the reference resistor 16 (temperature sensor) for measuring the ambient temperature on the surface side of the silicon substrate 11 formed in a predetermined shape. An insulating film forming step for forming an insulating film 12 on the surface side of the silicon substrate 11 so as to cover the reference resistor 16 for measuring the ambient temperature, and a pair of thermopiles 14 and 15 ( A temperature sensor) and a conductive line forming step for forming the heaters 13 so as to be positioned between the pair of thermopiles 14 and 15, respectively, and a back surface side of the silicon substrate 11 is removed to form a diaphragm 12a on the back surface of the insulating film 12. Forming a diaphragm.

  According to such a manufacturing method, the base body becomes the insulating film 12, but even in such a case, since the reference resistor 16 is not directly exposed to the flow path R, the silicon substrate 11 can be detected efficiently.

(A) is a conceptual diagram of the flow measurement device according to one embodiment of the present invention, (B) is a schematic cross-sectional view of a flow sensor used in the flow measurement device according to one embodiment of the present invention. It is a top view of the flow sensor used for the flow measuring device concerning one embodiment of the present invention. An example of the manufacturing method of the flow sensor of this invention is shown, (A)-(H) is explanatory drawing which showed the manufacturing process of the flow sensor in time series. (A) is a perspective view of the principal part in the middle of the manufacturing process of a flow sensor, (B) is an expanded sectional view of the principal part. An example of the manufacturing method of the flow sensor of this invention is shown, (A)-(G) is explanatory drawing which showed the manufacturing process of the flow sensor in time series. An example of the conventional thermal type flow sensor is shown, (A) is a plan view of the conventional flow sensor, and (B) is a sectional view of the conventional flow sensor.

Explanation of symbols

10 Flow sensor 11 Silicon substrate (base)
12 Insulating thin film (insulating film)
12a Diaphragm 13 Heater 14 Upstream thermopile (temperature sensor)
15 Downstream thermopile (temperature sensor)
16 Reference resistance (temperature sensor for ambient temperature measurement)

Claims (4)

  A pair of temperature sensors provided on the surface side of the substrate and positioned on the upstream side and the downstream side in the fluid flow direction; a heater provided on the surface side of the substrate and positioned between the pair of temperature sensors; A flow sensor comprising: a temperature sensor for measuring an ambient temperature provided on the base so as not to directly contact the fluid.   The flow sensor according to claim 1, wherein the temperature sensor for measuring the ambient temperature is provided on a back surface side of the base body. Having an insulating film covering the surface of the substrate; and
The flow sensor according to claim 1, wherein the temperature sensor for measuring the ambient temperature is provided so as to be interposed between the base body and the insulating film.   A pair of temperature sensors on the surface side of the substrate, a conduction line forming step for forming a heater so as to be positioned between the pair of temperature sensors, and a temperature sensor for measuring ambient temperature so as not to be in direct contact with the fluid An ambient temperature sensor forming step formed on the base body.

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