JPH04369480A - Semiconductor flow rate detector - Google Patents

Abstract

PURPOSE:To obtain the title detector excellent in flow rate detecting accuracy, the response to the fluctuation of a flow rate and response after a power supply is closed. CONSTITUTION:In a heating semiconductor chip 12, a heating element 2 wherein a plurality of NPN transistors are connected in parallel and the heating temp. detection element 3 positioned on the free end side of said element 2 and having three diodes connected thereto in series are formed and the thickness of the substrate of the heating semiconductor chip 12 at the part of the heating element 2 is made less than that of the part of the heating temp. detection element 3 to lower a thermal time constant. The heating semiconductor chip 12 is supported in a cantilevered fashion at one end part thereof by a heat insulating support and electrically connected to a lead frame within the support member by wire bonding.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor flow rate detection device for measuring the intake air amount of an engine, and more particularly to improvements in the structure of its heat generating semiconductor chip and the method of mounting the chip.

0002

2. Description of the Related Art Generally, in electronically controlled fuel injection systems for automobile engines, it is important to accurately measure the amount of air intake into the engine in order to control the air-fuel ratio. Conventionally, vane type air flow rate detection devices have been mainstream, but recently, thermal type flow rate detection devices that are small, can obtain a mass flow rate, and have good responsiveness are becoming popular. The flow rate detection element of this thermal flow rate detection device is formed by depositing or printing a temperature-sensitive resistance film such as platinum on a ceramic substrate.Since the detection element is formed on the ceramic substrate, it is strong against vibrations, etc. However, fine processing of the detection element and substrate was not possible, and there were limits to detection accuracy and responsiveness. Recently, photocopying,
A semiconductor flow rate detection device has also been proposed in which a detection element is formed on a semiconductor substrate using a semiconductor manufacturing process such as diffusion or etching.

FIGS. 13 and 14 show, for example, Japanese Patent Laid-Open No. 59-14
1 shows a sensor section of a conventional semiconductor flow rate detection device disclosed in Japanese Patent No. 7221. FIG. 13 is a partial cross-sectional perspective view of the sensor section;
FIG. 14 is a plan view of the heat generating semiconductor chip. In FIG. 13, 11 is a semiconductor chip for intake air temperature detection in which an intake air temperature detection element is formed on a silicon substrate, and 12 is a heat generation semiconductor chip in which a heating element and a heat generation temperature detection element are formed on a silicon substrate. 46 is a ceramic substrate on which a conductive paste is printed and fired so as to electrically connect the lead frame 32 and the semiconductor chips 11 and 12;
Semiconductor chips 11 and 12 are soldered using the flip chip bump method. The ceramic substrate 46 is housed in a casing 47 having a bellmouth-shaped entrance. As shown in FIG. 14, the heat generating semiconductor chip 12 includes a heat generating element 2 made of a diffused resistor and a heat generating temperature detecting element made of five diodes connected in series on a silicon substrate 10. Although not shown, the intake air temperature detection semiconductor chip 11 also has an intake air temperature detection element formed of a diode on a silicon substrate, similar to the heat generation semiconductor chip 12.

In the semiconductor type flow rate detection device configured as described above, the temperature detected by the heat generation temperature detection element 2 on the heat generation semiconductor chip 12 is determined by the temperature detected by the heat generation temperature detection element 2 on the heat generation semiconductor chip 12.
A heating current is supplied to the heating element 2 so that the temperature is a certain value higher than that detected by the upper intake air temperature detection element, and the air flow rate is detected by measuring the voltage corresponding to this heating current.

[0005]

[Problems to be Solved by the Invention] Conventional heat-generating semiconductor chips have both ends soldered to a substrate made of alumina ceramic or the like with high thermal conductivity, and because the bump size is relatively large, the heat-generating semiconductor chips are soldered to ceramic substrates. Thermal conduction loss increases. For this reason, there are problems such as low flow rate detection sensitivity, a long time until an accurate flow rate signal is obtained after power is turned on, and poor responsiveness to flow rate fluctuations.

The present invention has been made to solve the above-mentioned problems, and aims to provide a semiconductor flow rate detection device that is excellent in flow rate detection accuracy, responsiveness to flow rate fluctuations, and responsiveness after power is turned on. purpose.

[0007]

[Means for Solving the Problems] A semiconductor flow rate detection device of the present invention includes a heat generating element installed in a flow path, a heat generating semiconductor chip on which a heat generating temperature detecting element is formed, and an intake air temperature detecting element. constant temperature control for controlling the amount of heat generated by the heating element so that the temperature detected by the intake air temperature detection semiconductor chip and the heating temperature detection element is a certain temperature higher than the fluid temperature detected by the intake air temperature detection element; It is equipped with a circuit, and at least one end of the heat generating semiconductor chip is supported and fixed by a heat insulating support member.

Further, the heat generating semiconductor chip is provided with a heat generating temperature detecting element closer to the free end than the heat generating element.

Further, the thickness of the substrate of the heat generating semiconductor chip is such that the part where the heat generating element is formed is thinner than the part where the heat generating temperature detecting element is formed.

[0010] Furthermore, a thermal insulation layer was formed between the heating element and the supporting portion of the heating semiconductor chip.

Furthermore, polycrystalline silicon was used for the substrate of the heat generating semiconductor chip.

[0012] A second heating element is formed on the heating semiconductor chip between its support portion and the heating element, and the temperature of the second heating element is set to be lower than the heating element and higher than the fluid temperature by a predetermined temperature. It was heated electrically so that

[0013]

[Operation] The semiconductor flow rate detection device of the present invention has a structure in which at least one end of the heat generating semiconductor chip is cantilever-supported by the heat insulating support member, so that heat conduction loss from the heat generating semiconductor chip to the support portion is reduced. This improves flow rate detection accuracy, responsiveness to flow rate fluctuations, and responsiveness after power is turned on.

[0014] Further, a heat generating temperature detecting element is formed on the heat generating semiconductor chip on the free end side of the heat generating element, or a second heat generating element is formed between the support part of the heat generating semiconductor chip and the heat generating element, Since the second heating element was electrically heated to a temperature lower than the heating element and a predetermined temperature higher than the fluid temperature, changes in heat conduction loss from the heating semiconductor chip to the support member due to the flow rate, and temperature distribution in the longitudinal direction. changes due to flow rate are reduced, and responsiveness to flow rate fluctuations is improved.

Furthermore, since the thickness of the substrate of the heat generating semiconductor chip is made such that the part where the heat generating element is formed is thinner than the part where the heat generating temperature detecting element is formed, the thermal time constant of the heat generating temperature detecting element can be adjusted to match the heat of the heat generating element. It can be made larger than the time constant, and the temperature recovery in the heat generating temperature detecting element is delayed when the flow rate fluctuates, an excessive current is supplied to the heat generating element, and the flow rate signal tends to resonate slightly. This resonance characteristic can be used to correct the delay in the transient characteristics of the sensor. That is, the responsiveness can be improved by delaying the response of the heat generating temperature detecting element to provide resonance.

Since a thermal insulation layer is formed between the heat generating element and the supporting part of the heat generating semiconductor chip, or polycrystalline silicon is used for the substrate of the heat generating semiconductor chip, heat is not transferred from the heat generating element to the support member. Conduction loss can be further reduced, and flow rate detection accuracy and responsiveness are improved.

[0017]

[Example] Example 1. Embodiments of the present invention will be described below with reference to the drawings. First, FIGS. 1(a) and 1(b) show a heat generating semiconductor chip related to a semiconductor flow rate detection device according to a first embodiment of the present invention, where (a) is a plan view and (b) is a schematic cross-sectional view. . 2 in the figure is a plurality of NPNs formed in a silicon substrate.
A heating element 3 is formed by connecting transistors in parallel, and 3 is a heating temperature detecting element formed by connecting three diodes in series, which is arranged on the free end side of the heating element 2 of the heating semiconductor chip 12 supported on a cantilever as will be described later. will be established. Reference numeral 4 denotes a concave portion, which is formed so that the thickness of the substrate at the heat generating element 2 portion is thinner than at the heat generating temperature detecting element portion. 10 is a p-type substrate, 20 is an n-type substrate
type epitaxial layer, 21 is an n+ buried diffusion layer, 2
2 is a p-type diffusion layer, 23 is an n+ diffusion layer, 24 is a protective film,
25 is an aluminum wiring, and 26 is a bonding pad.

Next, a method of manufacturing this heat generating semiconductor chip will be explained based on FIG. 1(b). First, a polished flat p-type substrate 10, in this case has a resistivity of 0.05Ωm,
A highly conductive n+ layer is partially diffused at the positions where the heat generating element 2 and the heat generating temperature detecting element 3 are to be formed on the p-type substrate 10 having a diameter of 100 mm and a thickness of 0.25 mm to form an n+ buried diffusion layer 21. . This is formed to reduce the collector series resistance from the collector contact to the collector active region directly under the base region. Next, 0.005Ωm,
An n-type epitaxial layer 20 having a thickness of 10 μm and a donor concentration of 1022 m −3 is grown on a p-type substrate 10 in a direction in which the crystal structure is continuous with the base material and becomes a single crystal. Next, the n-type epitaxial layer 20 is oxidized and a window is opened by a mask-etch process through which the p-type is isolated and diffused to form an island of the n-type epitaxial layer 20, in which the base of the transistor and the diode are formed. A p-type diffusion layer 22 serving as a base is formed by diffusion. Also, the emitter,
N+ diffusion is performed in the collector terminal portion to form an n+ diffusion layer 23. Furthermore, a protective film 24 of silicon dioxide or nitride film (Si3N4) is formed on the surface of the substrate by thermal oxidation or thermal decomposition. Thereafter, a circuit wiring pattern is formed by aluminum evaporation and photolithography to form aluminum wiring 25 and bonding pads 26. Note that a window is opened in the silicon glass portion on the bonding pad 26 to make an external connection to the circuit. After the metal wiring process is completed, an inert insulating protective film is formed on the chip surface using SiO2 or silicon glass, generally called S glass, grown by thermal decomposition. The main components are formed on the semiconductor substrate through the above steps, and then a recess 4 is formed by etching using, for example, a KOH etching solution at a position corresponding to at least the heating element 2 on the back surface of the substrate, and a recess 4 of 3 mm x 14 mm is formed using a dicer. The heat generating semiconductor chip 12 is completed by dividing into chips.

The mounting method and structure of the heat generating semiconductor chip described above will be described with reference to FIGS. 2 and 3. Figure 2 (a
)(b) shows the sensor part of this flow rate detection device,
(a) is a plan sectional view, and (b) is a side sectional view. Similar to the heat generating semiconductor chip 12, the intake air temperature detection semiconductor chip 11 has an intake air temperature detection element made of a diode or a diffused resistor formed on a silicon substrate, and is placed adjacent to the heat generating semiconductor chip 12. By installing the intake air temperature detection semiconductor chip 11 on the upstream side and in the same plane as the heat generation semiconductor chip 12 as shown in the figure,
A vortex is generated downstream of the semiconductor chip for detecting the intake air temperature, and the semiconductor chip 1 generates heat from dust contained in the fluid, for example, the air.
2. It has the effect of reducing anchoring and accumulation on the upstream end face. The intake air temperature detection semiconductor chip 11 and the heat generation semiconductor chip 12 are bonded and cantilevered at one end to a pedestal 33 made of glass with silver paste or adhesive, and the pedestal 33 is fixed to a resin base 31. There is. base 3
1 is sealed with a lead frame 32, and a pad provided at one end of the lead frame 32 and the semiconductor chip 1 are sealed.
A bonding wire 30 connects bonding pads 1 and 12. Furthermore, the base 31 and cap 34
Glue and filler such as gel or epoxy resin inside 3
5 is included. In this embodiment, the base 31, the pedestal 3
3, the cap 34 and the filler 35 constitute a heat insulating support member.

FIGS. 3(a) and 3(b) show a sensor duct in which the above-mentioned sensing element of this device is installed, where (a) is a left side view and (b) is a front sectional view. The intake air temperature detection semiconductor chip 11 and the heat generation semiconductor chip 12 are installed in the detection duct 41 so that their longitudinal direction is substantially perpendicular to the flow, and the lead frame 32 is connected to the electronic circuit 44. There is. A mesh-like net 43 is provided on the upstream side of the detection duct for the main purpose of rectifying the flow, such as making the flow velocity distribution uniform. Arrows indicate the direction of fluid inflow.

Next, the operating circuit will be explained using the electronic circuit diagram shown in FIG. In the figure, a portion surrounded by a dashed line shows a heat generating semiconductor chip 12, in which a diode 3 as a heat generating temperature detecting element and a transistor 2 as a heat generating element are formed. A bridge circuit is constituted by a diode 7 as an intake air temperature detection element formed in the intake air temperature detection semiconductor chip, a diode 3 as an exothermic temperature detection element formed in the heat generation semiconductor chip, and fixed resistors 51 to 53. ing. A constant voltage is supplied from a constant voltage circuit composed of a power supply 65, a fixed resistor 54, and a Zener diode 64 to the bridge circuit and the transistor 62 having a current mirror configuration.
and 63. An amplifier 70, fixed resistors 55, 56, 58, 59, and a phase compensation capacitor 61 constitute an amplifier circuit to amplify the bridge circuit output voltage. The output of the amplifier 70 is connected to the transistor 2 via a fixed resistor 57, and is converted into an emitter current of the transistor 2, which is a heating element. transistor 63
By connecting a resistor 60 to the collector of a transistor 62 having the same specifications as the above, a voltage corresponding to the emitter current can be detected at the output terminal 66.

A method of operating the detection circuit configured as above will be described. The base-emitter voltage VBE of the diode is generally expressed as a linear function of the absolute temperature T by Equation 1.

[0023]

[Math 1]

Here, V0 shows a value of about 1.27 V as VBE at absolute temperature zero, and α is a voltage temperature coefficient, which depends on the emitter current but shows a value of about -2.4 mV/K. By connecting a plurality of diodes in series, the temperature sensitivity of the voltage is increased and the voltage is boosted so that it falls within the input common mode voltage range of the amplifier. Assuming that the gain of the bridge amplifier circuit is sufficiently large, the following relational expression holds true when the bridge circuit is in a balanced state.

[0025]

[Math 2]

[0026] However, R2 and R3 are the resistance values of the bridge resistors 52 and 53, VB is the bridge voltage, and VH
is the voltage across the diode 3 which is a heating element, VK is the voltage across the diode 7 which is a temperature detection element, and is expressed by the equation 1.
From the equation, it is expressed by equations 3 and 4.

[0027]

[Math 3]

[0028]

[Math 4]

Here, TK indicates the absolute temperature at the intake air temperature detection element of the intake air temperature detection chip, and TH indicates the absolute temperature at the heat generation temperature detection element of the heat generating semiconductor chip. From Equations 1 to 4, temperature TH is given by Equation 5, which is a function of TK.

[0030]

[Math 5]

The circuit is configured to supply current to the heat generating element on the heat generating semiconductor chip so that the temperature of the heat generating temperature detecting element on the heat generating semiconductor chip becomes constant regardless of the flow rate.

On the other hand, a flat heat generating semiconductor chip is shown in FIG.
Calorific value P of the heating element when installed as shown in
The relationship between H and the flow velocity U is expressed by Equation 6 in an equilibrium state.

[0033]

[Math 6]

However, A and B are constants. Also, the calorific value P
H is the product of the collector-emitter voltage VCE of the heat generating transistor 2 and the load current IC, and is expressed by Equation 7.

[0035]

[Math 7]

Therefore, by configuring a circuit that keeps the VCE of the heat generating transistor and the temperature difference (TH-TK) constant, it becomes possible to detect the flow velocity U and flow rate from the load current IC. In the circuit shown in FIG. 4, the transistors 62 and 63 form a current mirror circuit, so that a current equivalent to the load current IC of the heat generating transistor 2 is taken out as a voltage output at the resistor 60.

The temperature distribution in the longitudinal direction of the heat generating semiconductor chip of the semiconductor type flow rate detection device is shown in the characteristic diagram of FIG. Figure 5 (
(a) shows the temperature distribution when the heat generating temperature detecting element of Example 1 configured as above is formed on the free end side of the heat generating element, and (b) shows the temperature distribution when the heat generating temperature detecting element of the comparative example is formed on the free end side of the heat generating element. This is the temperature distribution when formed on the fixed end side. The vertical axis represents the temperature, and the horizontal axis represents the distance from the free end of the heat generating semiconductor chip.The characteristic curve H represents the temperature distribution at a large flow rate, and the characteristic curve L represents the temperature distribution at a small flow rate. (a) (b) Both heat generation temperature detection elements operate at the same temperature. Figure 5 (a
) and (b), it is clear that in (b) the temperature distribution characteristic of the heat generating semiconductor chip changes more with the flow rate. This is because the heat conduction loss from the heating element of the heating semiconductor chip to the support portion is larger than that from the heating element to the free end side. Therefore, it is better to form the heat generating temperature detection element on the free end side of the heat generating element on the heat generating semiconductor chip.
The temperature change of the heating element when the flow rate fluctuates is reduced, and the response time is also reduced.

The semiconductor flow rate detection device of the present invention configured as described above includes a heating element 2, a temperature detection element 3,
Since semiconductors such as transistors and diffused resistors are used in 7, a general bipolar semiconductor process can be used, which is excellent in mass production, and since the heating element 2 and the substrate are made of the same material, silicon, there is no problem of thermal stress. The characteristics of the element can be obtained. In addition, the heat-generating semiconductor chip 12 is cantilever-supported at one end by a heat-insulating support member, and the heat-generating temperature detection element 3 is provided closer to the free end than the heat-generating element 2. Heat conduction loss to components can be reduced, and flow rate detection accuracy, responsiveness to flow rate fluctuations, and responsiveness after power is turned on are improved. In addition, since the substrate thickness of the heat generating semiconductor chip 12 is made thinner in the part where the heat generating element 2 is formed than in the part where the heat generating temperature detecting element 3 is formed, the response of the heat generating temperature detecting element 3 on the heat generating semiconductor chip 12 is It is possible to improve responsiveness by delaying the delay and providing resonance. Furthermore, since the heating element 2 is configured by connecting multiple transistors in parallel, the resistance around the emitter is reduced, the heat distribution (temperature) within the heating element 2 is made uniform, and the high current capacity and good performance are achieved. A heat generating transistor with high frequency characteristics can be realized. and semiconductor chip 11,1
2 is mounted on a lead frame 32 inside the support member using a bonding wire 30 with a small contact area, which reduces heat conduction loss from the heat generating semiconductor chip 12 to the support part, and also makes the sensor easy to handle. It also has excellent productivity.

Example 2. 6(a) and 6(b) show a heat generating semiconductor chip 12 in which diffused resistors are used for the heat generating element 2 and the heat generating temperature detecting element 3 according to the second embodiment of the present invention.
(a) is a plan view, and (b) is a schematic cross-sectional view. A diffused resistor consisting of a p-type diffusion layer 22 is formed on the island 20 of the n-type epitaxial layer by the same process as in Example 1 described above, and the surface acceptor concentration is around 1024 m-3 and the depth is several μm.
, area resistance 100-200Ω/□, resistance temperature coefficient 100
It is in the range of 0 to 3000 ppm/°C. The temperature of the heat generating temperature detecting element 3 is detected as a change in the diffused resistance, and the heating current of the diffused resistor which is the heat generating element is controlled so as to keep the temperature constant. The positional relationship between the heat generating element 2 and the heat generating temperature detecting element 3 is the same as in the first embodiment, and similar effects are achieved.

Example 3. 7(a) and 7(b) show a heat generating semiconductor chip according to Embodiment 3 of the present invention.
(a) is a plan view, and (b) is a schematic cross-sectional view. In this embodiment, the heat conductivity between the heat generating element 2 of the heat generating semiconductor chip 12 and the supporting portion is 1/50 that of single crystal silicon, for example.
A thermal insulating layer 28 made of oxidized porous silicon or the like as described below is formed, thereby reducing heat conduction loss to the support portion. After selective masking with a nitride film, this porous silicon oxide undergoes an anodic reaction in an HF solution.
and can be formed by oxidation reactions. This thermal insulating layer increases the ratio of heat transfer to the fluid to the amount of heat generated in the heating element 2, improving flow sensitivity and providing good responsiveness to flow rate fluctuations.

Example 4. FIGS. 8A to 8E are schematic cross-sectional views showing, in order of steps, a method of manufacturing a heat generating semiconductor chip using a polycrystalline silicon substrate instead of a P-type substrate according to Example 3 of the present invention. As shown in FIG. 8A, an n+ buried diffusion layer is first formed on the surface of the n-type substrate 29, and an insulating film 27 is partially formed on the surface as an etching mask material. After that, etching is performed from the top surface to form a V-shaped groove on the surface, and an insulating film 27 is created by surface oxidation (Fig. 8
b). Next, as shown in FIG. 8(c), a thick polycrystalline silicon 6 is grown in vapor phase on the insulating film 27, which is an oxide film. Furthermore, the wafer is turned over and polished until the insulating film 27 appears on the surface of the n-type substrate 29, thereby forming separation pockets as shown in FIG. 8(d). A heat generating element 2 and a heat generating temperature detecting element 3 are manufactured in the pocket by the same masking process and diffusion process as in Example 1 (FIG. 8e).

The electrical characteristics of the polycrystalline silicon substrate 6 are not important, and its main purpose is to mechanically support the wafer by utilizing the fact that its thermal conductivity is about 1/3 that of single crystal silicon. . By using polycrystalline silicon for the substrate of the heat generating semiconductor chip 12, heat conduction loss from the heat generating element 2 to the support portion is reduced, flow sensitivity is improved, and good responsiveness to flow rate fluctuations can be obtained.

Example 5. 9(a) and 9(b) show a heat generating semiconductor chip 12 in which a second heat generating element 9 is formed between a heat generating element 2 and a support portion according to a fifth embodiment of the present invention. is a plan view, and (b) is a schematic cross-sectional view. The second heating element 9 is made of a p-type diffused resistor and is formed within an island of the n-type epitaxial layer 20. The operation circuit of the second heating element 9 will be explained using the electronic circuit diagram of FIG. 10. A current equivalent to that of the heating element 2 flows through the transistor 67, and heat is generated by Joule heat in the resistor 9, which is the second heating element. The temperature of the second heating element 9 is set to be lower than that of the heating element 2 and higher than the fluid temperature by a predetermined temperature. The amount of heat generated PH2 in the second heating element is expressed by Equation 8.

[0044]

[Math. 8]

However, R9 represents the resistance value of the diffused resistor 9, which is the second heating element. As is clear from comparing Equations 7 and 8, the ratio of the amount of heat generated PH2 in the second heating element 9 to the amount of heat generated PH2 in the heating element 2 increases as the flow rate increases. On the other hand, the temperature of the support portion of the heat generating semiconductor chip 12 becomes lower as the flow rate increases, as shown in FIG. 5(a). Therefore, by causing the heating element 2 to generate heat due to collector loss, forming the second heating element 9 on the supporting portion of the heat generating semiconductor chip, and generating heat using Joule heat, the dependence of the temperature of the supporting portion on the flow rate can be significantly reduced. Flow rate sensitivity is improved and good responsiveness to flow rate fluctuations can be obtained.

[0046] By forming a bridge circuit with the diffused resistor of the second heating element 9 and the diffused resistor which is the intake air temperature detecting element on the semiconductor chip 11 for detecting the intake air temperature, and performing the known constant temperature difference control, has a similar effect.

Example 6. Note that in the above embodiment, the chip 11
, 12 are fixed to the base 31 via the pedestal 33 with an adhesive. However, as shown in FIG. 11, which is a schematic cross-sectional view showing another embodiment of the sensing section according to the present invention, the heat generating semiconductor chip 12 is mounted on the die pad 36. The sensing portion may be created by performing die bonding, further wire bonding, and then transfer molding the bonding portion.

Example 7. There is also a method of connecting and fixing the heat generating semiconductor chip 12 and the inner leads 32 by a bump method, as shown in FIG. 12, which is a schematic cross-sectional view showing still another embodiment of the sensing section according to the present invention. Au bumps 39 are provided on the bonding pads 26 of the heat generating semiconductor chip 12 using photolithography and electroplating, and the TAB tape is made by bonding inner leads 32 and a tape 37 made of polyimide resin with an adhesive. There is. All the bumps are pressed together using a heated bonding tool on the inner lead 32 of the TAB tape to bond the Au.
/Sn alloy, and then the bonding part and T
One end of AB is molded and sealed by transfer molding.

By creating the sensing portion using TAB technology and transfer molding technology as described above, the supporting strength of the heat generating semiconductor chip 12 is further increased, and the thickness of the molding material that is the supporting material for the heat generating semiconductor chip 12 is reduced. It can be made thinner, smaller and lighter, and manufacturing can be automated. Furthermore, assembly of the sensing section into the detection duct becomes easy.

Embodiment 8 In the above embodiment, the electronic circuit 44 was installed in the housing provided on the outer periphery of the duct 40, but a semiconductor chip in which the electronic circuit part except the adjustment resistor was integrated was installed on the base 31. The electronic circuit 44 can be significantly downsized by connecting the semiconductor chips 11, 12 and the lead frame 32 by wire bonding, or by integrating the electronic circuit and the intake air temperature detection element on the heat generating semiconductor chip.
Improves noise resistance and reduces costs.

[0051]

As described above, the semiconductor type flow rate detection device of the present invention has a heat-generating semiconductor chip in which a heat-generating temperature detecting element and a heat-generating element made of a semiconductor element are formed on a silicon substrate, and is thermally supported at one end thereof. Since the structure is cantilever-supported by members, the thermal stress generated in the heat-generating temperature detection element is small, reducing heat conduction loss to the support part, improving flow rate detection accuracy, responsiveness to flow rate fluctuations, and responsiveness after power is turned on. As well as improving durability against vibrations and the like.

Furthermore, by forming the heating element and the heating temperature detecting element on the heating semiconductor chip in close proximity to each other, the heating element is formed on the supporting portion side of the heating semiconductor chip, and the heating temperature detecting element is formed on the free end side of the heating semiconductor chip. The change in heat conduction loss to the member due to the flow rate is reduced, that is, the change in the temperature distribution in the longitudinal direction of the chip with respect to the flow rate is reduced, and responsiveness is improved.

Furthermore, by making the thickness of the substrate of the heating semiconductor chip in the portion where the heating element is formed thinner than the substrate thickness in the portion where the heating temperature detecting element is formed, the thermal time constant of the heating element is reduced to a value equal to that of the temperature detecting element. This makes it possible to give resonance to the response characteristics to flow rate fluctuations and improve response delays.

[0054] Then, a heat insulating layer is arranged on the support side of the heat generating element, polycrystalline silicon is used as the substrate of the heat generating semiconductor chip, or another second heat generating element is provided on the support side of the heat generating element. Thereby, heat conduction loss from the heating element to the support portion can be reduced. This increases flow rate detection sensitivity and improves responsiveness to flow rate fluctuations. Furthermore, the time required for the heating element to reach a predetermined temperature and to obtain an accurate flow rate signal after the electronic circuit is powered on is also shortened.

[Brief explanation of drawings]

FIG. 1 is a plan view and a schematic cross-sectional view of a heat generating semiconductor chip related to a semiconductor flow rate detection device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a sensing section according to Example 1 of the present invention.

FIG. 3 is a side view and a sectional view of a semiconductor flow rate detection device according to a first embodiment of the present invention.

FIG. 4 is an electronic circuit diagram according to Embodiment 1 of the present invention.

FIG. 5 is a characteristic diagram showing the temperature distribution in the longitudinal direction of the heat generating semiconductor chip according to Example 1 of the present invention together with a comparative example.

FIG. 6 is a plan view and a schematic cross-sectional view of a heat generating semiconductor chip according to Example 2 of the present invention.

FIG. 7 is a plan view and a schematic cross-sectional view of a heat generating semiconductor chip according to Example 3 of the present invention.

FIG. 8 is a schematic cross-sectional view sequentially showing the manufacturing process of a heat generating semiconductor chip according to Example 4 of the present invention.

FIG. 9 is a plan view and a schematic cross-sectional view of a heat generating semiconductor chip according to Example 5 of the present invention.

FIG. 10 is an electronic circuit diagram according to a fifth embodiment of the present invention.

FIG. 11 is a schematic cross-sectional view of a sensing section in which a heat generating semiconductor chip according to a sixth embodiment of the present invention is mounted.

FIG. 12 is a schematic cross-sectional view of a sensing section in which a heat generating semiconductor chip according to a seventh embodiment of the present invention is mounted.

FIG. 13 is a partially sectional perspective view of a sensor section of a conventional semiconductor flow rate detection device.

FIG. 14 is a plan view of a semiconductor chip of a conventional semiconductor flow rate detection device.

[Explanation of symbols]

2 Heating element 3 Heat generation temperature detection element 6 Polycrystalline silicon substrate 9 Second heating element 11 Semiconductor chip for intake air temperature detection 12 Semiconductor chip for heat generation 28 Thermal insulation layer 30 Bonding wire 31 Base 32 Lead frame 33 Pedestal 34 Cap 35 Filling material 44 Electronic circuit

Claims (6)

[Claims] 1. A heat generating semiconductor chip installed in a flow path and having a heat generating element and a heat generation temperature detection element formed thereon, a semiconductor chip for intake air temperature detection installed in the flow path and having an intake air temperature detection element formed thereon, and A semiconductor flow rate detection device comprising a constant temperature control circuit that controls the amount of heat generated by the heat generation element so that the temperature detected by the heat generation temperature detection element is a certain temperature higher than the fluid temperature detected by the intake air temperature detection element. A semiconductor flow rate detection device characterized in that at least one end of a heat generating semiconductor chip is supported and fixed by a heat insulating support member. 2. The semiconductor flow rate detection device according to claim 1, wherein the heat generation semiconductor chip is provided with a heat generation temperature detection element closer to the free end than the heat generation element. 3. The substrate thickness of the heat generating semiconductor chip is such that the portion where the heat generating element is formed is thinner than the portion where the heat generating temperature detecting element is formed.
3. The semiconductor flow rate detection device according to item 1 or 2. 4. The semiconductor flow rate detection device according to claim 1, further comprising a heat insulating layer formed between the heat generating element and the support portion of the heat generating semiconductor chip. . 5. The semiconductor flow rate detection device according to claim 1, wherein polycrystalline silicon is used for the substrate of the heat generating semiconductor chip. 6. A second heating element is formed in the heating semiconductor chip between its support portion and the heating element, and the second heating element is set at a temperature lower than the heating element and higher than the fluid temperature by a predetermined temperature. 6. The semiconductor flow rate detection device according to claim 1, wherein the semiconductor flow rate detection device is electrically heated to .