JP6532810B2 - Flow sensor - Google Patents

Description

  The present invention relates to a flow sensor.

  Currently, as a flow sensor provided in an electronically controlled fuel injection device of an internal combustion engine such as a car, a thermal flow sensor manufactured by MEMS (Micro Electro Mechanical Systems: Micro-Electro-Mechanical Systems) technology can reduce costs and reduce costs. It is noted because it can be driven by electric power.

  As background art of this technical field, there are patent 5 210491 (patent documents 1) and JP, 2012-78228, A.

  According to Japanese Patent No. 5210491 (Patent Document 1), when the heating resistor and the temperature measuring resistor are formed of the same material in the same substrate, when the bridge circuit is formed of the resistors, only the heating resistor is thermally degraded at high temperature. The issue is described in which the balance of the lead bridge circuit changes and leads to a decrease in flow rate accuracy. As a countermeasure to this, by adding a low temperature heating resistor between the heating resistor and the temperature measuring resistor and forming the temperature measuring resistor and the bridge circuit, the temperature can be accurately measured by the heating resistor with little thermal degradation. It is described that it can be monitored and can maintain high performance for a long time.

  Further, in JP 2012-78228 A (Patent Document 2), the upstream side heating resistor and the downstream side heating are provided by providing three terminals in the heating resistor and energizing the heating resistor through these terminals. A technology that generates a calorific value difference with the resistor and differentiates the thermal influence that the upstream temperature-measuring resistor receives from the heating resistor and the thermal influence that the downstream-side temperature measuring resistor receives from the heating resistor Is described. Thereby, it is possible to freely change the temperature difference-flow rate characteristic which is the reference of the flow rate measurement, and to offset the shift of the detection value due to the application error.

Patent No. 5210491 JP 2012-78228 A

  For example, when a thermal type flow sensor having a heat generating resistor, an upstream temperature measuring resistor, and a downstream temperature measuring resistor is used in an internal combustion engine such as an automobile, for example, in most states where the internal combustion engine is driven. Because the downstream temperature measuring resistor has a temperature as high as that of the heating resistor, the downstream temperature measuring resistor is greatly affected by heat, and the downstream temperature measuring resistor has a higher temperature than the upstream temperature measuring resistor. The change in resistance value depending on the elapsed time becomes larger. Therefore, there is a concern that the zero point at which the output of the bridge circuit composed of the upstream temperature measuring resistor and the downstream temperature measuring resistor is adjusted to no wind changes with the elapsed time and the flow accuracy decreases.

  In order to solve the above problems, the flow rate sensor according to the present invention is an upstream temperature measuring resistor provided on the upstream side of the first heating resistor, separated from the first heating resistor and the first heating resistor. And a downstream temperature-measuring resistor provided on the downstream side of the first heating resistor at a distance from the first heating resistor, and a second heat-generating resistor provided on the upstream temperature-measuring resistor via an insulator. And a resistor. Then, the second heating resistor is heated by power supply to heat the upstream temperature measuring resistor, and the difference between the resistance value of the upstream temperature measuring resistor and the resistance value of the downstream temperature measuring resistor is within the allowable range. By doing this, the flow rate sensor's zero point correction is performed.

  According to the present invention, a highly sensitive and highly accurate flow rate sensor can be realized.

  Problems, configurations, and effects other than those described above will be apparent from the description of the embodiments below.

FIG. 5 is a plan view of the main part of the sensor chip according to the first embodiment. It is principal part sectional drawing of the sensor chip in the AA 'line | wire of FIG. It is a principal part top view of a sensor module provided with the sensor chip of FIG. It is principal part sectional drawing of the sensor module in the BB 'line | wire of FIG. FIG. 1 is a cross-sectional view of an essential part of an intake passage of an internal combustion engine to which a thermal fluid flow sensor according to a first embodiment is attached. FIG. 10 is a cross-sectional view of main parts of a sensor chip according to a modification of the first embodiment. FIG. 1 is a circuit diagram of a thermal fluid flow sensor according to a first embodiment. FIG. 6 is an operation flow diagram of the thermal fluid flow sensor when the thermal fluid flow sensor according to the first embodiment is incorporated into a vehicle. In the thermal type fluid flow sensor by Example 1, it is a graph which shows the relationship of the heating temperature and heating time which the constant resistance change at the time of heating a resistance temperature sensor directly is carried out. FIG. 7 is a plan view of the main part of a sensor chip according to a second embodiment. It is principal part sectional drawing of the sensor chip in the CC 'line | wire of FIG. FIG. 18 is a cross-sectional view of main parts of a sensor chip according to a third embodiment. FIG. 18 is a plan view of the essential parts of a sensor chip according to a fourth embodiment. It is principal part sectional drawing of the sensor chip in the DD 'line | wire of FIG. FIG. 20 is a cross-sectional view of main parts of a sensor chip according to a fifth embodiment. FIG. 18 is a cross-sectional view of main parts of a sensor chip according to a modification of the fifth embodiment.

  In the following embodiments, when it is necessary for the sake of convenience, it will be described by dividing into a plurality of sections or embodiments, but unless specifically stated otherwise, they are not unrelated to each other, one is the other And some or all of the variations, details, and supplementary explanations.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), it is particularly pronounced and clearly limited to a specific number in principle. It is not limited to the specific number except for the number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps and the like) are not necessarily essential except in the case where they are particularly clearly shown and where they are considered to be obviously essential in principle. Needless to say.

  In addition, when we say “consists of A”, “consists of A”, “have A”, and “include A”, except for those cases where it is clearly stated that it is only that element, etc., the other elements are excluded. It goes without saying that it is not something to do. Similarly, in the following embodiments, when referring to the shapes, positional relationships and the like of components etc., the shapes thereof are substantially the same unless particularly clearly stated and where it is apparently clearly not so in principle. It is assumed that it includes things that are similar or similar to etc. The same applies to the above numerical values and ranges.

  Further, in the drawings used in the following embodiments, even a plan view may be hatched to make the drawing easy to see, and even a sectional view may be hatched to make the drawing easy to see. is there. Further, in the cross-sectional view and the plan view, the size of each portion does not correspond to the actual device, and a specific portion may be displayed relatively large in order to make the drawing easy to understand. Further, even when the sectional view and the plan view correspond to each other, a specific part may be displayed relatively large in order to make the drawing easy to understand.

  Further, in all the drawings for describing the following embodiments, components having the same function are denoted by the same reference symbols in principle, and the repetitive description thereof will be omitted. Hereinafter, the present embodiment will be described in detail based on the drawings.

  A thermal fluid flow sensor according to the first embodiment will be described. The thermal fluid flow rate sensor according to the first embodiment is a thermal resistance thermal fluid flow rate sensor that detects the fluid flow rate using the characteristic that the resistance value of the resistor changes with temperature.

<Structure of Thermal Type Fluid Flow Sensor>
The structure of the thermal fluid flow sensor according to the first embodiment will be described with reference to FIGS. 1 to 5. FIG. 1 is a plan view of an essential part of a sensor chip according to a first embodiment. FIG. 2 is a cross-sectional view of an essential part of the sensor chip taken along line A-A 'of FIG. FIG. 3 is a plan view of an essential part of a sensor module provided with the sensor chip of FIG. FIG. 4 is a cross-sectional view of a main part of the sensor module taken along line B-B ′ of FIG. 3. FIG. 5 is a cross-sectional view of an essential part of an intake passage of an internal combustion engine to which the thermal fluid flow rate sensor according to the first embodiment is attached.

  As shown in FIGS. 1 and 2, the sensor chip 1 of the thermal fluid flow sensor includes a semiconductor substrate 2 made of single crystal Si (silicon) and a diaphragm part where a portion of the semiconductor substrate 2 has been removed for flow detection. And 9.

  On the semiconductor substrate 2, the first heating resistor 3 via the first insulating film 10, the upstream temperature measuring resistor 4 disposed on the upstream side of the first heating resistor 3, and the first heating resistor 3 A downstream temperature measuring resistor 5 disposed on the downstream side of the first heat generating resistor 7 and a first heat generating resistor temperature measuring resistor 7 for measuring the temperature of the first heat generating resistor 3 are formed. The temperature measuring resistor 7 for the first heating resistor is between the first heating resistor 3 and the upstream temperature measuring resistor 4 and between the first heating resistor 3 and the downstream temperature measuring resistor 5 respectively. It is arranged.

  The first heat-generating resistor 3, the upstream temperature-measuring resistor 4, the downstream temperature-measuring resistor 5 and the temperature-measuring resistor 7 for the first heat-generating resistor are covered with the second insulating film 11, and the upstream temperature-measuring A second heating resistor 6 made of, for example, the same material as the first heating resistor 4 is formed above the resistor 4 via the second insulating film 11. That is, a part of the second heat generating resistor 6 overlaps the upstream temperature measuring resistor 4 in plan view. The second heating resistor 6 is covered by the third insulating film 12. The second heating resistor 6 may be formed of a material different from that of the first heating resistor 3.

  The first insulating film 10, the second insulating film 11, and the third insulating film 12 are, for example, a single layer film made of silicon oxide, a single layer film made of silicon nitride, a laminated film in which silicon oxide and silicon nitride are stacked, or silicon oxide And silicon nitride alternately.

  In addition, the second insulating film 11 and the third insulating film 12 are removed for external input / output, and each resistor (the first heat generating resistor 3, the upstream temperature measuring resistor 4, the downstream temperature measuring resistance) It has a plurality of electrode pads 8 in which a part of each of the body 5, the second heat generating resistor 6, and the first heat generating resistor temperature measuring resistor 7) is exposed. In order to improve the wire bonding described later, each resistor (the first heating resistor 3, the upstream temperature-measuring resistor 4, the downstream temperature-measuring resistor 5, the second heating resistor 6, and the first heating resistor) A metal film made of, for example, Al (aluminum) may be provided on each of the electrode pads 8 of the body temperature measuring resistor 7).

  Furthermore, an organic insulating film may be formed on the third insulating film 12, and in this case, at least each resistor (the first heat generating resistor 3, the upstream temperature measuring resistor 4, the downstream resistance temperature measuring resistor 5) The organic insulating film above the second heating resistor 6 and the temperature measuring resistor 7 for the first heating resistor is removed, or the entire organic insulating film above the diaphragm portion 9 is removed.

  The second heating resistor 6 is closer to the upstream temperature-measuring resistor 4 than the first heating resistor 3 and is provided in a place where the heat transfer is good, for example, above the upstream temperature-measuring resistor 4 There is. In the first embodiment, since the second heating resistor 6 is provided above the upstream-side temperature measuring resistor 4 via the second insulating film 11, the thickness of the second insulating film 11 The distance between the heating resistor 6 and the upstream temperature measuring resistor 4 is determined. The thickness T1 of the second insulating film 11 sandwiched between the upper surface of the first insulating film 10 and the lower surface of the third insulating film 12 is, for example, in the range of 0.1 μm to 1 μm.

  Further, the upstream-side temperature measuring resistor 4 and the downstream-side temperature measuring resistor 5 are provided so as to be axisymmetric in the flow direction of the intake air sandwiching the first heat generating resistor 3, whereby no air flow occurs. The heat distribution of the upstream-side temperature measuring resistor 4 and the heat distribution of the downstream-side temperature measuring resistor 5 in the above are equal.

  In the first embodiment, the sensor chip 1 is exemplified in which a part of the second heat generating resistor 6 overlaps the upstream temperature measuring resistor 4 in a plan view, but the present invention is not limited to this. Is not a required condition. The middle point of the straight line connecting the first heating resistor 3 and the second heating resistor 6 is positioned upstream of the middle point of the straight line connecting the upstream temperature-measuring resistor 4 and the downstream side temperature-measuring resistor 5 As long as the second heating resistor 6 is formed, the second heating resistor 6 may be formed. The same applies to Examples 2 and 3 described later.

  Next, as shown in FIG. 3 and FIG. 4, the sensor module 13 has a support substrate 14 and a recess 15 formed in the support substrate 14.

  The sensor chip 1 is fixed by an adhesive 16 inside the recess 15, and the control circuit chip 17 is mounted on the support substrate 14 other than the area where the recess 15 is formed. Further, the electrode pads 18 of a part of the control circuit chip 17 and the electrode pads 8 of the sensor chip 1 are electrically connected via bonding wires 19a. Further, the other part of the electrode pads (electrode pads for input / output terminals to the outside) 18 of the control circuit chip 17 and the external input / output terminals 20 formed on the support substrate 14 are connected via bonding wires 19b. Are connected electrically.

  Since the electrode pad 8 of the sensor chip 1 and the electrode pad 18 of the control circuit chip 17 are easily corroded, the electrode pad 8, the electrode pad 18 and the control circuit chip 17 are covered with a corrosion preventing resin 21.

  Since the diaphragm portion 9 is a fluid detection portion, the surface side of the diaphragm portion 9 is not covered with the corrosion preventing resin 21, and the back side of the diaphragm portion 9 fixed to the support substrate 14 is an adhesive 16. So that the diaphragm 9 is not sealed.

  Next, as shown in FIG. 5, the thermal fluid flow sensor 22 includes a body 23, a sub passage 24 formed in the body 23, a support 25 for fixing the sensor module 13, and a support cover 26. And.

  The sensor module 13 is fixed to the thermal fluid flow sensor 22 by the support 25 and the support cover 26 so that the intake air 29 flows to the diaphragm portion 9 of the sensor chip, which is the intake flow rate detecting portion of the sensor module 13 . Further, the thermal type fluid flow rate sensor 22 is attached to the intake pipe 27 so as to penetrate and is provided to the intake pipe 27 so that the intake 29 flowing to the main passage 28 is taken into the sub passage 24. Although FIG. 5 shows the auxiliary passage 24 in parallel and linearly simplified with the intake pipe 27, the auxiliary passage 24 may have a curved or branched shape in the body 23. Good.

  In the first embodiment, as shown in FIG. 2, the second heating resistor 6 is formed on the upstream-side temperature measuring resistor 4 via the second insulating film 11, but the invention is limited thereto. It is not a thing.

  For example, as shown in FIG. 6, the second heating resistor 6 is formed on the first insulating film 10, the second heating resistor 6 is covered with the second insulating film 11, and the first heating resistor 6 is formed on the second insulating film 11. The heating resistor 3, the upstream-side temperature measuring resistor 4, the downstream-side temperature measuring resistor 5, and the temperature measuring resistor 7 for the first heating resistor may be formed. In this case, the upstream temperature measuring resistor 4 is disposed above the second heating resistor 6 via the second insulating film 11. That is, a part of the second heat generating resistor 6 overlaps the upstream temperature measuring resistor 4 in plan view.

  Alternatively, although not shown, the second heat-resistant material in the same layer as the first heat-generating resistor 3, for example, a high melting point metal, is disposed closer to the upstream temperature-measuring resistor 4 than the first heat-generating resistor 3. The heating resistor 6 may be formed.

<Operation flow of thermal fluid flow sensor>
The operation flow of the thermal fluid flow sensor according to the first embodiment will be described with reference to FIGS. 7 and 8. FIG. 7 is a circuit diagram of the thermal fluid flow sensor according to the first embodiment. FIG. 8 is an operation flow diagram of the thermal fluid flow sensor when the thermal fluid flow sensor according to the first embodiment is incorporated into a vehicle.

  As shown in FIG. 7, the temperature of the first heating resistor 3 is monitored by the temperature measuring resistor 7 for the first heating resistor, and the controller 34 controls the voltage or current so as to reach a desired temperature. The upstream temperature-measuring resistor 4 and the downstream temperature-measuring resistor 5 form a bridge circuit with the bridge resistor 30 provided in the sensor chip other than the diaphragm or in the control circuit chip, and the upstream temperature-measuring resistor A predetermined voltage (Vref) is applied between 4 and the downstream temperature measuring resistor 5. After connecting the voltage difference between the middle point of the upstream temperature-measuring resistor 4 and the bridge resistor 30 and the middle point of the downstream temperature-measuring resistor 5 and the bridge resistor 30 to the amplifier 31, the analog / digital converter (ADC) 33 and the like are converted into digital data and output to an electronic control unit (ECU) 36.

  In the first embodiment, after the amplifier 31, a comparator 32 for determining whether the zero point is within the allowable range is provided, and when it is out of the allowable range, the second heating resistor 6 is provided. A voltage is applied to heat the upstream-side temperature measuring resistor 4.

  In the initial windless state, the resistance values of the upstream temperature-measuring resistor 4, the downstream temperature-measuring resistor 5 and the bridge resistor 30 in the state of being heated by the first heating resistor 3 are designed to be equal. The output to the control device 36 becomes zero, and the correlation between the flow rate of the intake air and the differential voltage is converted by the analog / digital converter 33 based on this state and output.

  Next, the operation flow of the thermal fluid flow sensor will be described. In the following description of the operation flow, the circuit diagram of the thermal fluid flow sensor shown in FIG. 7 will be referred to as appropriate. According to the operation flow shown in FIG. 8, the fluid flow rate is output, for example, by a thermal fluid flow rate sensor incorporated in the electronic control fuel injection device of the automobile.

  First, before starting an automobile engine, power is supplied to the thermal fluid flow sensor and the electronic control unit 36 (step S1). Before starting the engine means, for example, a state in which a key is only inserted into a key cylinder.

  Next, the zero point at the time of no wind is confirmed by the comparator 32, and it is determined whether the zero point is within the allowable range (step S2).

  If it is within the allowable range (OK), the engine is started (step S3). Then, the intake flows (step S4), and the intake flow rate is output (step S5).

  In the case of out of tolerance (NG), the second heating resistor 6 is instantaneously supplied with power, and after the power supply of the second heating resistor 6 is stopped (step S6), the zero point is confirmed again by the comparator 32 It is determined whether the zero point is within the allowable range (step S2). That is, the operation flow of the thermal fluid flow sensor in the first embodiment has the zero point correction mode in which the zero point can be within the allowable range.

  Although the above description exemplifies the case of starting the first engine of the automobile according to the operation flow shown in FIG. 8, the present invention is not limited to this. For example, in an automobile equipped with an idle stop function, the engine is stopped when the automobile stops at a signal or the like, and then the engine is restarted. Also in this case, the zero point can be corrected according to the operation flow shown in FIG.

  Also, as another operation mode, the zero point is confirmed by the comparator 32, and if it is out of the allowable range, the upstream side temperature measuring resistor 4 and the downstream side temperature measuring resistor 5 are calculated from the varied differential voltage. The second heat generating resistor 6 is minutely heated by the amount of change in resistance. Then, the zero point is confirmed again by the comparator 32, and after correcting the zero point within the allowable range, the temperature of the second heating resistor 6 is fixed and the engine is started while supplying power, and the intake flow rate is output. .

  Moreover, although the resistance value of the upstream-side resistance temperature detector 4 and the resistance value of the downstream-side resistance temperature detector 5 are designed to be equal to each other, due to variations in manufacturing and reliability tests before shipment, etc. Thermal fluid flow sensors may be manufactured in which the zero point in windless conditions exceeds an acceptable range. Also for such a thermal type fluid flow rate sensor, the balance between the resistance value of the upstream temperature measuring resistor 4 and the resistance value of the downstream temperature measuring resistor 5 is improved by using the second heating resistor 6 As a result, since the zero point can be corrected, the manufacturing yield of the thermal fluid flow sensor is improved and the manufacturing cost is reduced.

<The effect of the thermal fluid flow sensor of this embodiment>
The effect of the thermal fluid flow sensor according to the first embodiment will be described with reference to FIGS. 1 and 9. FIG. 9 is a graph showing the relationship between the heating temperature and the heating time required for constant resistance change (several ohms) when the resistance temperature detector is directly heated in the thermal fluid flow rate sensor according to the first embodiment.

  As shown in FIG. 9, by raising the heating temperature to 100 ° C., the heating time can be reduced to about 1/10.

  In the operation flow shown in FIG. 8, in the thermal fluid flow rate sensor, the resistance change of the downstream temperature measuring resistor 5 progresses faster than the upstream temperature measuring resistor 4 due to the heating of the first heat generating resistor 3 with the use time. Therefore, the zero point fluctuates. In order to correct the zero point, when the heating temperature of the second heating resistor 6 is equal to the heating temperature of the first heating resistor 3, the upstream temperature measuring resistor has the same time as the usage time of the thermal fluid flow sensor Although it is necessary to heat only 4, it requires heating for a long time, which causes problems in flow rate detection.

  Therefore, in the first embodiment, the heating temperature of the second heating resistor 6 is at least higher than the heating temperature of the first heating resistor 3, and the resistance value of the downstream temperature measuring resistor 5 is upstream in a short time. The resistance value of the side resistance temperature detector 4 is brought close to correct the zero point within the allowable range. For example, when the first heating resistor 3 is heated at 200 ° C., by heating the second heating resistor 6 at 500 ° C., it becomes possible to correct the zero point in a time of about 1 / 1,000. .

  In addition, in the operation mode shown in FIG. 8, since the zero point is confirmed each time the engine is started, the change in resistance value is small (for example, less than 1 Ω) even when out of the allowable range. It is not necessary to heat the body 6 for a long time. Furthermore, by making the pattern (area for heat generation) of the second heat generating resistor 6 smaller than the pattern (area for heat generation) of the first heat generating resistor 3, power consumption is suppressed and the zero point is efficiently corrected. Is possible.

  As described above, according to the first embodiment, the fluctuation of the zero point of the thermal fluid flow sensor can be instantaneously suppressed within the allowable range regardless of the operating time of the engine, so that the flow accuracy of the thermal fluid flow sensor can be improved. It is possible to maintain the reliability of the thermal fluid flow sensor.

  The difference between the sensor chip 1A according to the second embodiment and the sensor chip 1 according to the first embodiment is that the second heat generating resistor 6 is disposed above the downstream temperature-measuring resistor 5 via the second insulating film 11. The same resistor 35 is formed.

  The structure of the sensor chip according to the second embodiment will be described with reference to FIGS. 10 and 11. FIG. FIG. 10 is a plan view of the main part of the sensor chip according to the second embodiment. FIG. 11 is a cross-sectional view of main parts of the sensor chip taken along line C-C ′ of FIG.

  The residual stress in the diaphragm portion 9 changes depending on the laminated material. Therefore, when the second heating resistor 6 is formed only on the upstream side temperature measuring resistor 4 via the second insulating film 11, the balance of the residual stress of the sensor chip 1A may be deteriorated.

  However, as shown in FIGS. 10 and 11, the resistor 35 is formed above the downstream temperature measuring resistor 5 with the second insulating film 11 interposed therebetween, thereby sandwiching the first heating resistor 3. Since symmetry can be maintained in the structure on the upstream side and the downstream side, the balance of the residual stress of the sensor chip 1A is improved. Thus, the strength of the diaphragm 9 can be improved, and the reliability of the sensor chip 1A can be improved.

  In plan view, a part of the resistor 35 overlaps the downstream temperature-measuring resistor 5, and the second heating resistor 6 and the resistance are arranged so as to be axisymmetric in the flow direction of intake air across the first heating resistor 3. The body 35 is provided.

  Also, the resistor 35 has an independent electrode pad 8 and is usually connected to the ground. However, in the sensor chip 1A, since the second heating resistor 6 and the resistor 35 are provided so as to be axisymmetric in the flow direction of intake air across the first heating resistor 3, the intake direction is reversed. Even when the specification is changed to the mounting specification, it is possible to obtain the effect of suppressing the variation of the zero point of the thermal fluid flow sensor within the allowable range only by changing the connection of the resistor 35 and the connection of the second heat generating resistor 6 it can.

  Alternatively, the resistor 35 can be used as a third heating resistor, and can be heated independently of the second heating resistor 6 to correct the zero point when there is no wind.

  The difference between the sensor chip 1B according to the third embodiment and the sensor chip 1 according to the first embodiment is that the first heat generating resistor 3 is formed of a high heat resistant material in the same layer as the second heat generating resistor 6. It is that you are. The high heat resistant material is, for example, a high melting point metal such as W (tungsten) or Mo (molybdenum).

  The structure of the sensor chip according to the third embodiment will be described with reference to FIG. FIG. 12 is a cross-sectional view of main parts of a sensor chip according to a third embodiment.

  As shown in FIG. 12, on the semiconductor substrate 2, an upstream-side temperature-measuring resistor 4 disposed on the upstream side via the first insulating film 10, and a downstream-side temperature-measuring resistor 5 disposed on the downstream side , For the first heat generating resistor disposed between the upstream temperature measuring resistor 4 and the downstream temperature measuring resistor 5 along the upstream temperature measuring resistor 4 and the downstream temperature measuring resistor 5, respectively A temperature resistor 7 is formed. The upstream-side temperature measuring resistor 4, the downstream-side temperature measuring resistor 5, and the first heating resistor temperature measuring resistor 7 are covered with a second insulating film 11.

  The first heating resistor 3, the second heating resistor 6, and the resistor 35 are formed on the second insulating film 11, and the second heating resistor 6 is formed above the upstream temperature measuring resistor 4 The resistor 35 is formed above the downstream temperature measuring resistor 5. That is, a part of the second heat generating resistor 6 overlaps the upstream temperature measuring resistor 4 in plan view, and a part of the resistor 35 overlaps the downstream temperature measuring resistor 4.

  Furthermore, between the second heating resistor 6 and the resistor 35, the first heating resistor 3 made of the same layer and the same material as the second heating resistor 6 is formed. The first heating resistor temperature measuring resistor 7 is disposed on the upstream side and the downstream side of the first heating resistor 3 in plan view.

  As described above, by forming the first heat generating resistor 3 in the same layer as the second heat generating resistor 6 and forming them with a highly heat-resistant material, resistance deterioration due to heat can be suppressed, so the sensor chip 1B Reliability can be improved.

  The difference between the sensor chip 51 according to the fourth embodiment and the sensor chip 1 according to the first embodiment is the temperature measurement method. The temperature measurement method according to the first embodiment described above is a thermal resistance method utilizing the characteristic that the resistance value changes with temperature. On the other hand, the temperature measurement method of the fourth embodiment is a thermocouple method using the temperature difference between the thermocouple on the semiconductor substrate (cold point) and the vicinity of the first heating resistor (warm point).

  The structure of the sensor chip according to the fourth embodiment will be described with reference to FIGS. 13 and 14. FIG. FIG. 13 is a plan view of an essential part of a sensor chip according to a fourth embodiment. FIG. 14 is a cross-sectional view of main parts of the sensor chip taken along line DD ′ of FIG.

  As shown in FIG. 13, a sensor chip 51 using a thermocouple has a semiconductor substrate 65 made of single crystal Si (silicon) and a diaphragm portion 64 from which a portion of the semiconductor substrate 65 has been removed for flow detection. .

  The first heat generating resistor 52 is provided on the semiconductor substrate 65 near the center of the diaphragm portion 64, and the upstream thermocouple 53 is arranged in line symmetry in the flow direction of the intake air with the first heat generating resistor 52 interposed therebetween. And the downstream thermocouple 54 are disposed. Further, the second heating resistor 55 is disposed above the upstream thermocouple 53, the resistor 56 is disposed above the downstream thermocouple 54, and the second heating resistor 55 and the resistor 56 The first heat generating resistor 52 is disposed so as to be line symmetrical in the flow direction of intake air.

  Further, it has a plurality of electrode pads 57 exposing a part of each of the first heating resistor 52, the upstream thermocouple 53, the downstream thermocouple 54, the second heating resistor 55, and the resistor 56, The plurality of electrode pads 57 are electrically connected to the control circuit chip through bonding wires. The upstream thermocouple 53 and the downstream thermocouple 54 output a differential voltage by the bridge circuit.

  As shown in FIG. 14, the upstream thermocouple lower layer wire 58 and the downstream thermocouple lower layer wire 59 are formed on the semiconductor substrate 65 via the first insulating film 66, and the upstream thermocouple lower layer wire 58 and the downstream thermocouple lower layer wire 59 are formed. The downstream thermocouple lower layer wire 59 is covered with the second insulating film 67.

  An upstream thermocouple upper layer wire 62 and a downstream thermocouple upper layer wire 63 are formed on the second insulating film 67, and an upstream thermocouple upper layer wire 62 is disposed above the upstream thermocouple lower layer wire 58, A downstream thermocouple upper layer wire 63 is disposed above the downstream thermocouple lower layer wire 59. The upstream thermocouple lower layer wire 58 and the upstream thermocouple upper layer wire 62 constitute an upstream thermocouple 53, and the downstream thermocouple lower layer wire 59 and the downstream thermocouple upper layer wire 63 constitute a downstream thermocouple 54 Be done.

  In the upstream thermocouple 53, a hot spot connection plug 60 and a cold spot connection plug (not shown) in which the upstream thermocouple lower layer wire 58 and the upstream thermocouple upper layer wire 62 penetrate the second insulating film 67 in the vertical direction. ) Are alternately connected. The numbers of the upstream thermocouple lower layer wires 58 and the upstream thermocouple upper layer wires 62 connected alternately are equal. Similarly, in the downstream thermocouple 54, the hot spot connection plug 60 and the cold spot connection plug 61 in which the downstream thermocouple lower layer wire 59 and the downstream thermocouple upper layer wire 63 penetrate the second insulating film 67 in the vertical direction. Are alternately connected. The numbers of downstream thermocouple lower layer wires 59 and downstream thermocouple upper layer wires 63 connected alternately are equal. Further, the upstream thermocouple 53 and the downstream thermocouple 54 are covered by the third insulating film 68.

  A first heating resistor 52, a second heating resistor 55, and a resistor 56 are formed on the third insulating film 68, and the second heating resistor 55 is disposed above the upstream thermocouple 53, A resistor 56 is disposed above the downstream thermocouple 54. A first heating resistor 52 is formed between the second heating resistor 55 and the resistor 56. Furthermore, the first heat generating resistor 52, the second heat generating resistor 55, and the resistor 56 are covered with a fourth insulating film 69. Although not shown, the fourth insulating film 69 is opened at the electrode pad 57.

  The first insulating film 66, the second insulating film 67, the third insulating film 68 and the fourth insulating film 69 are, for example, a single layer film made of silicon oxide, a single layer film made of silicon nitride, silicon oxide and silicon nitride Or a laminated film in which a plurality of silicon oxides and silicon nitrides are alternately stacked.

  In addition, a temperature measuring resistor for the first heating resistor or a thermocouple for the first heating resistor for measuring the temperature of the first heating resistor 52 is provided in the vicinity of the first heating resistor 52 to perform temperature control. It is also good.

  Also in the sensor chip 51 according to the fourth embodiment, the downstream side thermocouple 54 changes due to the influence of heat with use time. This is due to the resistance change of the downstream thermocouple lower layer wire 59 and the downstream thermocouple upper layer wire 63 due to the thermal effect. In particular, when a polycrystalline Si (silicon) film is used for the upstream thermocouple lower layer wire 58 and the downstream thermocouple lower layer wire 59, the gradient of the impurity concentration in the polycrystalline Si (silicon) film is due to the thermal effect. It occurs and the hot point shifts.

  However, even in such a case, the value of the upstream thermocouple 53 can be made close to the value of the downstream thermocouple 54 by heating the second heating resistor 55.

  The difference between the sensor chip 51A according to the fifth embodiment and the sensor chip 51 according to the fourth embodiment is that the first heating resistor 52, the first heating resistor 55 and the resistor 56 are different layers. It is forming. That is, the first heating resistor 55 is disposed between the upstream thermocouple upper wire 62 and the upstream thermocouple lower wire 58 of the upstream thermocouple 53, and the resistor 56 is disposed downstream of the downstream thermocouple 54. It is disposed between the thermocouple upper layer wire 63 and the downstream thermocouple lower layer wire 59.

  The structure of the sensor chip according to the fifth embodiment will be described with reference to FIG. FIG. 15 is a cross-sectional view of main parts of a sensor chip according to the fifth embodiment.

  As shown in FIG. 15, the upstream thermocouple lower layer wire 58 and the downstream thermocouple lower layer wire 59 are formed on the semiconductor substrate 65 via the first insulating film 66, and the upstream thermocouple lower layer wire 58 and the downstream thermocouple lower layer wire 59 are formed. The downstream thermocouple lower layer wire 59 is covered with a second insulating film 67.

  The second heating resistor 55 and the resistor 56 are formed on the second insulating film 67, and the second heating resistor 55 is disposed above the upstream thermocouple lower layer wiring 58, and the downstream thermocouple lower layer wiring A resistor 56 is disposed above 59. Further, the second heat generating resistor 55 and the resistor 56 are covered by the fifth insulating film 70.

  The upstream thermocouple upper layer wire 62 and the downstream thermocouple upper layer wire 63 are formed on the fifth insulating film 70, and the upstream thermocouple upper layer wire 62 is disposed above the second heating resistor 55, and the resistance A downstream thermocouple upper layer wire 63 is disposed above the body 56. The fifth insulating film 70 insulates the second heating resistor 55 from the upstream thermocouple upper layer wire 62, and the resistor 56 from the downstream thermocouple upper layer wire 63.

  In the upstream thermocouple 53, the hot spot connection plug 60 and the cold spot where the upstream thermocouple lower layer wire 58 and the upstream thermocouple upper layer wire 62 penetrate the second insulating film 67 and the fifth insulating film 70 in the vertical direction. The connection plugs (not shown) are alternately connected. The numbers of the upstream thermocouple lower layer wires 58 and the upstream thermocouple upper layer wires 62 connected alternately are equal. Similarly, in the downstream thermocouple 54, a hot-point connection plug 60 in which the downstream thermocouple lower layer wire 59 and the downstream thermocouple upper layer wire 63 penetrate the second insulating film 67 and the fifth insulating film 70 in the vertical direction. And cold point connection plugs 61 are alternately connected. The numbers of downstream thermocouple lower layer wires 59 and downstream thermocouple upper layer wires 63 connected alternately are equal. Further, the upstream thermocouple 53 and the downstream thermocouple 54 are covered by the third insulating film 68.

  The first heating resistor 52 is formed on the third insulating film 68, and the first heating resistor 52 is formed so as to be located between the upstream thermocouple 53 and the downstream thermocouple 54 in a plan view. There is. Furthermore, the first heat generating resistor 52 is covered by a fourth insulating film 69. Although not shown, the fourth insulating film 69 is opened at the electrode pad 57.

  By forming the second heat generating resistor 55 between the upstream thermocouple upper layer wire 62 and the upstream thermocouple lower layer wire 58 of the upstream thermocouple 53, the upstream thermocouple upper layer wire 62 and the upstream thermocouple can be obtained. Since the same amount of heat can be given to the lower layer wires 58, the power consumption of the second heating resistor 55 necessary for the correction of the zero point can be suppressed. Further, from the viewpoint of adjusting the residual stress in the diaphragm portion 64, the resistor 56 is also formed between the downstream thermocouple upper layer wire 63 of the downstream thermocouple 54 and the downstream thermocouple lower layer wire 59.

  In the fifth embodiment, although the first heating resistor 52 is formed on the third insulating film 68, the present invention is not limited to this.

  For example, as shown in FIG. 16, the first heat generating resistor 52 may be formed on the second insulating film 67 in the same layer as the second heat generating resistor 55, for example, a high heat resistant material made of high melting point metal. Even with the sensor chip 51B having such a structure, the power consumption of the second heating resistor 55 necessary for the correction of the zero point can be suppressed.

  As mentioned above, although the invention made by the present inventor was concretely explained based on an embodiment, the present invention is not limited to the above-mentioned embodiment, and can be variously changed in the range which does not deviate from the gist. Needless to say.

  The present invention includes at least the following embodiments.

[Supplementary Note 1]
A flow rate sensor for measuring the flow rate of a fluid to be measured, wherein
A first heating resistor,
A first temperature-measuring thermocouple provided on the downstream side of the first heating resistor at a distance from the first heating resistor;
A second temperature-measurement thermocouple, provided on the upstream side of the first heat-generating resistor, spaced apart from the first heat-generating resistor;
A second heating resistor provided to the second temperature measurement thermocouple via an insulator;
Have
The flow rate sensor which heats the second temperature-measuring thermocouple by the heat generation of the second heating resistor.

[Supplementary Note 2]
In the flow rate sensor described in the supplementary note 1,
The flow rate sensor, wherein a distance between the second heating resistor and the second temperature-measuring thermocouple is shorter than a distance between the first heating resistor and the second temperature-measuring thermocouple.

[Supplementary Note 3]
In the flow rate sensor described in the supplementary note 1,
The flow rate sensor, wherein the first temperature measurement thermocouple and the second temperature measurement thermocouple are formed of layers different from the first heating resistor.

[Supplementary Note 4]
In the flow rate sensor described in the supplementary note 1,
The flow rate sensor, wherein the first heating resistor and the second heating resistor are made of the same material.

[Supplementary Note 5]
In the flow rate sensor described in the supplementary note 1,
The flow rate sensor, wherein the first temperature measurement thermocouple and the second temperature measurement thermocouple are provided in line symmetry in the flow direction of the fluid to be measured with the first heating resistor interposed therebetween.

1, 1A, 1B sensor chip 2 semiconductor substrate 3 first heating resistor 4 upstream temperature-measuring resistor 5 downstream temperature-measuring resistor 6 second heating resistor 7 first temperature-measuring resistor resistance 8 electrode pad 9 diaphragm portion 10 first insulating film 11 second insulating film 12 third insulating film 13 sensor module 14 support substrate 15 concave portion 16 adhesive 17 control circuit chip 18 electrode pad 19a, 19b bonding wire 20 external input / output terminal 21 resin 22 Thermal type fluid flow sensor 23 body 24 sub passage 25 support 26 support cover 27 intake pipe 28 main passage 29 intake 30 bridge resistor 31 amplifier 32 comparator 33 analog / digital converter 34 controller 35 resistor 36 electronic control unit 51, 51A, 51B sensor chip 52 first heat generating resistor 53 upstream thermocouple 54 downstream thermocouple 55 second heating resistor 56 resistor 57 electrode pad 58 upstream thermocouple lower layer wire 59 downstream thermocouple lower layer wire 60 hot spot connection plug 61 cold spot connection plug 62 upstream thermocouple upper layer wire 63 downstream thermocouple upper layer wire 64 diaphragm portion 65 semiconductor substrate 66 first insulating film 67 second insulating film 68 third insulating film 69 fourth insulating film 70 fifth insulating film

Claims (15)

A flow rate sensor for measuring the flow rate of a fluid to be measured, wherein
A first heating resistor,
A first temperature measuring resistor provided on the downstream side of the first heating resistor at a distance from the first heating resistor;
A second temperature-measuring resistor provided on the upstream side of the first heating resistor at a distance from the first heating resistor;
A second heating resistor provided on the second temperature measuring resistor via an insulator;
Have
A flow rate sensor, which heats the second temperature measuring resistor by heat generation of the second heat generating resistor. In the flow rate sensor according to claim 1,
The flow rate sensor, wherein the distance between the second heating resistor and the second temperature measuring resistor is shorter than the distance between the first heating resistor and the second temperature measuring resistor. In the flow rate sensor according to claim 1,
The flow rate sensor, wherein the first heating resistor and the second heating resistor are made of the same material. In the flow rate sensor according to claim 1,
The flow rate sensor, wherein the heat generation area of the second heat generation resistor is smaller than the heat generation area of the first heat generation resistor. In the flow rate sensor according to claim 1,
The flow rate sensor, wherein the first temperature measuring resistor and the second temperature measuring resistor are provided in line symmetry in the flow direction of the fluid to be measured, sandwiching the first heating resistor. A flow rate sensor for measuring the flow rate of a fluid to be measured, wherein
A first heating resistor,
A first temperature measuring resistor provided on the downstream side of the first heating resistor at a distance from the first heating resistor;
A second temperature-measuring resistor provided on the upstream side of the first heating resistor at a distance from the first heating resistor;
A second heating resistor provided on the second temperature measuring resistor via an insulator;
Have
The second temperature measuring resistor is heated by the heat generation of the second heating resistor, and the difference between the first resistance value of the first temperature measuring resistor and the second resistance value of the second temperature measuring resistor is obtained. A flow sensor that corrects the zero point by keeping it within the allowable range. In the flow rate sensor according to claim 6,
The flow rate sensor, comprising a comparator that confirms a difference between the first resistance value and the second resistance value. In the flow rate sensor according to claim 6,
The fluid to be measured is the middle point of the straight line connecting the first heating resistor and the second heating resistor, and the middle point of the straight line connecting the first temperature measuring resistor and the second temperature measuring resistor. Located upstream of the flow sensor. In the flow rate sensor according to claim 6,
The flow rate sensor, wherein the distance between the second heating resistor and the second temperature measuring resistor is shorter than the distance between the first heating resistor and the second temperature measuring resistor. In the flow rate sensor according to claim 6,
The flow rate sensor, wherein the first heating resistor and the second heating resistor are made of the same material. In the flow rate sensor according to claim 6,
The flow rate sensor, wherein the heat generation area of the second heat generation resistor is smaller than the heat generation area of the first heat generation resistor. In the flow rate sensor according to claim 6,
The flow rate sensor, wherein the first temperature measuring resistor and the second temperature measuring resistor are provided in line symmetry in the flow direction of the fluid to be measured, sandwiching the first heating resistor. A flow rate sensor for measuring the flow rate of air taken into an internal combustion engine, comprising:
A first heating resistor,
A first temperature measuring resistor provided on the downstream side of the first heating resistor at a distance from the first heating resistor;
A second temperature-measuring resistor provided on the upstream side of the first heating resistor at a distance from the first heating resistor;
A second heating resistor provided on the second temperature measuring resistor via an insulator;
Have
In a state where the internal combustion engine is stopped, the second heating resistor is heated by power supply to heat the second temperature measuring resistor, and the first resistance value of the first temperature measuring resistor and the first resistance value are measured. (2) A flow sensor that corrects the zero point by setting the difference with the second resistance value of the resistance temperature detector within the allowable range. 14. The flow sensor according to claim 13, wherein
The flow rate sensor, comprising a comparator that confirms a difference between the first resistance value and the second resistance value. In the flow rate sensor according to claim 14,
The fluid to be measured is the middle point of the straight line connecting the first heating resistor and the second heating resistor, and the middle point of the straight line connecting the first temperature measuring resistor and the second temperature measuring resistor. Located upstream of the flow sensor.

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