JP6718363B2 - Humidity sensor and manufacturing method thereof - Google Patents

Description

The present invention relates to a humidity sensor and a manufacturing method thereof.

Japanese Patent No. 5406674 (Patent Document 1) is known as a technique for forming a sensor on a substrate such as a semiconductor substrate. In this patent document 1, a heating resistor for detecting an air flow rate, a temperature measuring resistor for a heating resistor and a temperature measuring resistor, and a humidity detecting heating resistor are arranged in a diaphragm formed on a semiconductor substrate. However, there is described a thermal fluid flow rate sensor in which a cavity layer and a protective film on the cavity layer are formed on the humidity detecting heating resistor, and the protective film is provided with a plurality of holes reaching the cavity layer. .. It is described that, by this, the air flow rate detection and the humidity detection can be formed on one substrate, and the cost can be reduced.

Further, in JP-A-2014-16177 (Patent Document 2), when the heater portion is rapidly heated, a large temperature difference occurs between the heater portion and the insulating layer, and the heater portion is peeled or cracked due to local thermal stress. It is described that there is a problem that causes a decrease in reliability. As a countermeasure against this, a thermal stress relaxation layer formed of a material having a high thermal conductivity is placed between the heater section and the insulating layer in contact with the heater section, whereby peeling due to local thermal stress can be suppressed and long-term It is described that the reliability of the information can be improved.

Patent No. 5406674 JP, 2014-16177, A

In recent years, in order to improve the fuel efficiency of internal combustion engines such as automobiles, it is necessary for the intake pipe to detect not only the amount of intake air but also the humidity and pressure of intake air.

In particular, a thermal resistance type humidity sensor element having a heater manufactured by a MEMS (Micro Electro Mechanical Systems) technique using a semiconductor is capable of highly accurate humidity detection in a high temperature environment, and It is attracting attention because it can reduce costs.

However, in the above-mentioned technique, the temperature distribution of the heater at the time of humidity detection is not taken into consideration, and in the above Patent Document 1, the heater has a structure covered with an insulating film, and the heater is heated. The temperature of the central portion of the heater region becomes high, and the temperature decreases as the distance from the central portion of the heater increases, and the temperature distribution in the heater region increases. As a result, there is a problem that the difference in the amount of water vaporized in the heater region becomes large and the variation in detection sensitivity becomes large. Since the temperature distribution in the heater region is also easily affected by the ambient temperature change, even a slight air flow in which intake air is replaced causes a greater variation in detected values.

In the above-mentioned Patent Document 2, since the heater portion and the stress relaxation layer having good thermal conductivity are in contact with each other, the temperature distribution in the region of the heater portion is small, but the entire stress relaxation layer (volume) is formed by the heater portion. There is a problem in that it has to be heated to a constant temperature and power consumption increases. Further, since the distance between the stress relaxation layer and the substrate is not taken into consideration, heat conduction to the substrate may make the boundary of the humidity detection region unstable, resulting in a decrease in detection accuracy.

An object of the present invention is to provide a technique in a humidity sensor in which a difference between a temperature distribution in a heater region and a set temperature can be reduced, and the humidity sensor can be less affected by a change in ambient temperature to reduce power consumption. It is in.

The above objects and novel features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

The following is a brief description of the outline of the typical embodiment of the embodiments disclosed in the present application.

A humidity sensor according to an embodiment is provided with a support substrate having a hollow portion, a first heater arranged on the support substrate, and an upper surface side or a lower surface side of the first heater. A heat uniform layer having a heat conductivity equal to or higher than a heat conductivity, and an insulating layer disposed between the first heater and the heat uniform layer. Further, the first heater and the heat uniform layer are arranged in the region of the insulating film on the cavity, and the heat uniform layer is arranged so as to overlap with the first heater in a plan view. 1 Humidity is measured using the change in voltage output from the heater.

A method of manufacturing a humidity sensor according to one embodiment includes (a) a step of providing an insulating film on a supporting substrate, (b) a step of forming a heater made of a metal film on the insulating film, and a wiring connected to the heater, (C) A step of forming a heat uniform layer on the heater via an insulating layer and a wiring connected to the heat uniform layer. The method further includes (d) a step of forming another insulating film on the heat uniform layer, and (e) a step of forming a cavity in a region of the support substrate below the heater. Further, the heat uniform layer has a heat conductivity equal to or higher than that of the heater, and the first heater and the heat uniform layer are arranged in a region of the insulating film on the cavity, In step c), the heat uniform layer is arranged so as to overlap the heater in a plan view.

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

It is possible to reduce the temperature difference of the temperature distribution in the humidity detection of the heater, and it is possible to realize a highly accurate and highly reliable humidity sensor.

It is a top view which shows the sensor chip in the thermal resistance type humidity sensor of Embodiment 1 of this invention. It is sectional drawing of the structure cut|disconnected along the AA line of FIG. FIG. 4 is a main-portion cross-sectional view showing the manufacturing process of the sensor chip in the thermal resistance-type humidity sensor which is Embodiment 1 of the present invention. FIG. 4 is a main-portion cross-sectional view showing the method for manufacturing the sensor chip of the thermal resistance-type humidity sensor, which is subsequent to FIG. 3; FIG. 5 is a main-portion cross-sectional view showing the method for manufacturing the sensor chip of the thermal resistance-type humidity sensor, which is subsequent to FIG. 4; FIG. 6 is a main-portion cross-sectional view showing the method for manufacturing the sensor chip of the thermal resistance-type humidity sensor, which is subsequent to FIG. 5; FIG. 7 is a main-portion cross-sectional view showing the method for manufacturing the sensor chip of the thermal resistance-type humidity sensor, which is subsequent to FIG. 6; It is the figure which compared Embodiment 1 of this invention, and the temperature profile of a comparative example. It is a figure which shows the relationship between the heater temperature and humidity detection voltage in Embodiment 1 of this invention. FIG. 1 is a schematic layout diagram showing a partially broken structure of a thermal air flow meter in which a thermal fluid flow sensor mounted in an intake passage of an internal combustion engine of an automobile is mounted according to a first embodiment of the present invention. FIG. 11 is a cross-sectional view of the sensor module taken along the line BB of FIG. 10. It is a principal part top view of the sensor chip in the thermal resistance type humidity sensor of Embodiment 2 of this invention. It is sectional drawing of the structure cut|disconnected along CC line of FIG. It is a figure which shows the temperature profile with respect to the distance from the heater center of a comparative example for every environmental temperature. It is a figure which shows the temperature profile with respect to the distance from the heater center of Embodiment 2 of this invention for every environmental temperature.

(Embodiment 1)
A humidity sensor according to an embodiment of the present invention will be described with reference to the drawings. The thermal resistance-type humidity sensor according to the first embodiment is a humidity sensor that detects absolute humidity using a heating resistor, and a constant voltage is applied to a low-heat generating antibody to generate a voltage output from the low-heat generating antibody. The humidity is measured using the change.

<Structure of thermal resistance humidity sensor>
FIG. 1 is a plan view showing a sensor chip of a thermal resistance type humidity sensor having a heater (first heater) 3 and a heat uniform layer 5 according to the first embodiment. Although FIG. 1 is a plan view, some parts are hatched to make the drawing easier to understand. As shown in FIG. 1, the sensor chip 1 includes a semiconductor substrate (support substrate) 2 made of single crystal silicon (Si), an insulating film (not shown) formed on the semiconductor substrate 2, and an insulating film on the insulating film. It has a heater 3 which is a low heat-generating antibody and is formed on the substrate 3, and wirings 4a and 4b for supplying power to the heater 3. Further, the heat uniform layer 5 for averaging the temperature distribution on the heater 3, the wiring 6 for preventing the heat uniform layer 5 from being charged up, and the electrodes 7a, 7b, 7c for connecting the wirings 4a, 4b, 6 to the outside, respectively. And have.

The heater 3 and the heat uniform layer 5 are arranged inside the diaphragm 8 which is the region of the insulating film formed by removing the semiconductor substrate 2 and at a position separated from the semiconductor substrate 2 by a certain distance. And, it is in a heat insulated state. Here, as described above, the region of the thin portion of the insulating film above the cavity 2a formed by partially removing the semiconductor substrate 2 is referred to as the diaphragm 8.

FIG. 2 is a cross-sectional view of the sensor chip 1 of FIG. 1 taken along the line AA.

The configuration of the main part of the sensor chip 1, which is a humidity sensor, will be described with reference to FIGS. 1 and 2. A semiconductor substrate 2 having a cavity 2a, a heater 3 arranged on the semiconductor substrate 2, and a heater 3 It has a heat uniform layer 5 provided on the upper surface side and having a heat conductivity equal to or higher than that of the heater 3, and an insulating layer 12a arranged between the heater 3 and the heat uniform layer 5. .. The heater 3 and the heat uniform layer 5 are arranged in the region of the insulating film on the cavity 2a. The heat uniform layer 5 is arranged so as to overlap the heater 3 in a plan view. That is, in a plan view, the heat uniform layer 5 is arranged so that at least a part thereof overlaps with the heater 3. Preferably, as shown in FIG. 1, the center NC of the heat uniform layer 5 and the center HC of the heater 3 are arranged. Both are arranged so that and match.

The heat uniform layer 5 is a layer having a thermal conductivity equal to or higher than that of the heater 3, and is also a thermal equilibrium layer. That is, the heat distribution of the layers on the heater 3 is made uniform. The heat uniform layer 5 is a layer made of an insulating film such as a metal film or a resin film, and preferably made of a metal film. At that time, the heat uniform layer 5 is preferably made of a metal film having a heat conductivity higher than that of the insulating layer 12a interposed between the heat uniform layer 5 and the heater 3. Further, the heat uniform layer 5 is preferably made of a metal film having a thermal conductivity higher than that of the heater 3, whereby the heat distribution of the layer on the heater 3 can be further uniformed.

The heat uniform layer 5 is preferably made of the same material as the heater 3. For example, the heat uniform layer 5 and the heater 3 are made of molybdenum (Mo). At that time, the thickness of the heat uniform layer 5 is preferably equal to or larger than the thickness of the heater 3. Further, the heat uniform layer 5 preferably has a size in plan view equal to or smaller than that of the heater 3.

The heat uniform layer 5 is electrically connected to the ground electrode to which the ground potential is supplied. That is, the electrode 7c electrically connected to the heat uniform layer 5 shown in FIG. 1 through the wiring 6 is a ground electrode to which a ground potential is supplied.

Moreover, as shown in FIG. 2, on the semiconductor substrate 2, the first insulating film 9, the second insulating film 10, the third insulating film 11, the fourth insulating film 12, and the fifth insulating film 13 are formed. , The sixth insulating film 14 and the seventh insulating film 15 are sequentially formed upward. That is, the insulating films are stacked upward.

The heater 3 is embedded in the fourth insulating film 12 on the third insulating film 11, while the heat uniform layer 5 is embedded in the fifth insulating film 13 on the fourth insulating film 12. The insulating layer 12a in the fourth insulating film 12 is disposed between the heater 3 and the heat uniform layer 5. That is, the heat uniform layer 5 is arranged on the heater 3 via the insulating layer 12a. In other words, the heat uniform layer 5 is arranged in another insulating layer (fourth insulating film 12) made of the same material as the insulating layer 12a. However, the insulating film in which the heater 3 and the heat uniform layer 5 are embedded may be another insulating film on the semiconductor substrate 2, and is not limited to the above insulating film or the above other insulating film.

Further, the wirings 4a and 4b shown in FIG. 1 for supplying power to the heater 3 are arranged on the third insulating film 11 on the semiconductor substrate 2, and the fourth insulating film is provided thereon as shown in FIG. The heat uniform layer 5 and the wiring 6 are formed via 12. Furthermore, a fifth insulating film 13, a sixth insulating film 14, and a seventh insulating film 15 are sequentially stacked on top of this, and the wiring 4b is electrically connected to the electrode 7b via a connecting portion (contact portion) 16. It is connected.

As described above, the heater 3 and the heat uniform layer 5 are located in the diaphragm 8 which is the region of the insulating film above the cavity 2a formed by removing the semiconductor substrate 2, and It is located at a distance. For example, as shown in FIG. 1, the distance L between the semiconductor substrate 2 and the heat uniform layer 5 in plan view is longer than the width W of the heat uniform layer 5 or the width of the heater 3 in plan view (L>W).

Further, both the heat uniform layer 5 and the heater 3 are made of a material having higher thermal conductivity than the insulating film (the first insulating film 9 to the seventh insulating film 15) including the insulating layer 12a. Then, the sensor chip 1 is formed by fixing the chip formed on the pedestal 17 with the adhesive 19. The pedestal 17 is provided with a ventilation hole 18 so that the diaphragm 8 is not sealed, and the adhesive 19 is formed so as not to block the ventilation hole 18. Further, in the first embodiment, the structure in which the ventilation hole 18 is opened in the lower surface is illustrated, but the ventilation hole 18 may be formed laterally by a groove or the like.

Next, a method of manufacturing the humidity sensor according to the first embodiment will be described in the order of steps with reference to FIGS. 3 to 7 are cross-sectional views of essential parts showing a process of manufacturing a sensor chip in the thermal resistance type humidity sensor according to the first embodiment of the present invention.

First, as shown in FIG. 3, a semiconductor substrate 2 made of single crystal Si and having a crystal orientation of Si<100> is prepared. Next, an insulating film is formed on the semiconductor substrate 2. That is, the first insulating film 9, the second insulating film 10 and the third insulating film 11 are formed on the semiconductor substrate 2. The first insulating film 9 is, for example, a silicon oxide film having a compressive stress formed by introducing oxygen or water vapor into a furnace body at 1000° C. or higher, and the second insulating film 10 is a CVD (Chemical) film. The silicon nitride film having tensile stress and the third insulating film 11 formed by the Vapor Deposition method are silicon oxide films having compressive stress using the CVD method.

Next, the third insulating film 11 which is a base insulating film is etched by about 15 nm by sputter etching using Ar gas to modify the surface, and then a metal film, for example, molybdenum (Mo) is formed by sputtering to a thickness of about 150 nm. The heater 3 of the humidity sensor, the wiring 4b connected to the heater 3 and the wiring 4a shown in FIG. 1 are formed by using the lithography method and the metal etching technique.

Next, as shown in FIG. 4, a fourth insulating film 12 is formed, and then planarized by CMP (Chemical Mechanical Polishing). The fourth insulating film 12 is a silicon oxide film having a compressive stress, which is formed by the CVD method. As a result, the heater 3 and the wiring 4b are covered with the fourth insulating film 12 (embedded in the fourth insulating film 12).

Then, the fourth insulating film 12 is etched by about 15 nm by sputter etching using Ar gas to modify the surface, and then a metal film, for example, molybdenum (Mo) is formed by about 150 nm by the sputtering method. Using the metal etching technique, the heat uniform layer 5 and the wiring 6 connected to the heat uniform layer 5 are formed. Thereby, the heat uniform layer 5 is arranged on the heater 3 via the insulating layer 12a of the fourth insulating film 12.

At this time, the heat uniform layer 5 is arranged (formed) so as to overlap the heater 3 in a plan view, as shown in FIG. Preferably, the heat uniform layer 5 is formed so that the center NC of the heat uniform layer 5 and the center HC of the heater 3 coincide with each other.

The metal film forming the heat uniform layer 5 may be W (tungsten), for example.

Next, another insulating film is formed on the heat uniform layer 5. Specifically, as shown in FIG. 5, the fifth insulating film 13 is formed, and then planarized by CMP to form the sixth insulating film 14 and the seventh insulating film 15. Note that the fifth insulating film 13 is a silicon oxide film having a compressive stress formed by a CVD method, the sixth insulating film 14 is a silicon nitride film having a tensile stress formed by a plasma CVD method, and a seventh insulating film 14 is formed. The insulating film 15 is a silicon oxide film having a compressive stress using the CVD method. Note that a heat treatment step may be appropriately added in order to adjust the stress of the metal film and the insulating film which have been formed so far.

Next, the connection portion 16 is formed in the insulating film on the wiring 4a and the wiring 4b connected to the heater 3 shown in FIG. 1 and the wiring 6 connected to the heat uniform layer 5 by using the photolithography method and the insulating film etching technology. .. Next, the seventh insulating film 15 is etched by about 15 nm by sputter etching using Ar gas to modify the surface, and then a metal film such as Ti, TiN, or TiW is formed by sputtering to a thickness of about 20 nm to 200 nm, After that, a laminated film containing aluminum (Al) as a main component is continuously formed. After that, the electrodes 7a, 7b and 7c shown in FIG. 1 are formed by the photolithography method and the metal etching technique.

Next, as shown in FIG. 6, in the first insulating film 9 and the second insulating film 10 formed on the back surface of the semiconductor substrate 2, the Si of the semiconductor substrate 2 in the region to be the diaphragm 8 shown in FIG. A mask for removing the film is formed by using a photolithography technique and an insulating film etching technique.

Next, as shown in FIG. 7, the Si film on the back surface side of the semiconductor substrate 2 is KOH (potassium hydroxide) using the first insulating film 9 and the second insulating film 10 on the back surface of the semiconductor substrate 2 as masks. The solution is removed by wet etching using a solution, TMAH (tetramethylamide) solution, or dry etching containing a fluorine-based gas as a main component to form the cavity 2a in the lower region of the heater 3. As a result, the diaphragm 8 which is a region of the insulating film is formed above the cavity 2a.

Note that a silicon nitride film and a silicon oxide film may be additionally formed in order to adjust the film stress of the entire diaphragm 8 after forming the third insulating film 11.

As described above, the heat uniform layer 5 has a heat conductivity equal to or higher than the heat conductivity of the heater 3, and the heater 3 and the heat uniform layer 5 are interposed in the region of the insulating film on the cavity 2a via the insulating layer 12a. The arranged sensor chip 1 is manufactured.

<Effect of Humidity Sensor of First Embodiment>
The thermal resistance type humidity sensor is characterized by high detection sensitivity at high temperature and high humidity as compared with a resistance type or a capacitance type using another moisture sensitive film.

FIG. 8 shows the temperature profile of the first embodiment based on the center of the heater in the line AA of FIG. 1 and the humidity sensor of the comparative example in which the heater has the same size and does not have a heat uniform layer. It is a figure which shows a temperature profile.

In FIG. 8, the size of the diaphragm 8 shown in FIG. 1 is 500 μm in both length and width, and the distance from the heater center HC to the semiconductor substrate 2 is 250 μm. The heater 3 is a quadrangle of 80 μm in both length and width (40 μm on each side), and the heat uniform layer 5 of the first embodiment has the same size as the heater 3. Here, in the case where the set temperature 100% converted from the heater resistance value is 500° C., temperature profiles of both Embodiment 1 (E) of FIG. 8 and Comparative Example (F) of FIG. 8 are compared. There is.

First, in Comparative Example (F), the temperature of the heater center HC is about 15% (t1) higher than the set temperature, the temperature decreases toward the outside of the heater, and the temperature of the heater end in the heater area HA increases. In the vicinity, it is below 100% by a few% (t0). That is, it can be seen that this is a temperature profile in which the temperature decreases radially from the center of the heater when viewed from above. Therefore, the temperature distribution (temperature difference) in the heater (heater area HA) is about 20% (ΔT1=t1+t0), and since the heater shape is quadrangular, the temperature of the heater corner portion further decreases. Since the heater is covered with a silicon oxide film having a low thermal conductivity and is separated from the Si substrate (semiconductor substrate) having a good thermal conductivity, the temperature outside the heater edge sharply decreases, It can be seen that at 40 μm from the edge (80 μm from the center of the heater), the temperature becomes 40% (about 200° C.) with respect to the set temperature, and the temperature further decreases toward the outside of the heater area HA.

On the other hand, in the first embodiment (E) shown in FIG. 8 in which the heater 3 and the heat uniform layer 5 have the same size, the temperature rise of the heater center HC can be suppressed to about 5% (t2). It can be seen that the temperature distribution in the inside can be less than 10% (ΔT2=t2+t0), and the temperature inside the heater can be made uniform by the heat uniform layer 5. Since the heat uniform layer 5 has the same size as the heater 3, the temperature profile outside the heater end (the end of the heat uniform layer 5) is the same as in the comparative example of (F), and the temperature drop (t0) is also (F). It becomes almost equal to the comparative example.

As a result of measuring the temperature profile by setting it to another heater temperature (converted to a heater resistance value), it has been confirmed that the temperature profiles calculated at the ratio corresponding to the set temperature are almost the same. It was also found that the temperature distribution in the heater area HA is reduced as the heat uniform layer 5 is larger than the heater 3, but the power consumption of the heater is increased accordingly. Therefore, the size of the heat uniform layer 5 is preferably equal to or slightly smaller than that of the heater 3. That is, by making the size of the heat uniform layer 5 equal to or slightly smaller than that of the heater 3, it is possible to suppress an increase in power consumption of the heater 3.

Next, FIG. 9 is a diagram showing the relationship between the heater temperature and the humidity detection voltage in the first embodiment of the present invention, where the ambient temperature is 85° C. and the relative humidity is 80% (water content in air is about 280 kg/m ³ ). The relationship between the heater temperature (resistance substitution calculation) and the humidity detection voltage (v) is shown.

As shown in FIG. 9, when the heater temperature is 300° C. or higher, the humidity detection voltage rapidly increases. That is, it can be seen that the higher the heater temperature, the higher the humidity detection voltage and the higher the detection sensitivity. In the comparative example (H) having no heat uniform layer, since the temperature distribution (ΔT1) is large, the humidity detection voltage is about ±30% or more (ΔV1) with respect to the setting in the humidity detection area of the heater part. I found that there were variations. On the other hand, the variation of the detected voltage according to the first embodiment (G) can be suppressed to ±10% or less (ΔV2) because the temperature distribution (ΔT2) can be reduced. The humidity detection voltage is the amount of heat consumed to evaporate the moisture in the air. If the temperature distribution in the heater surface is large, the air flow is disturbed by the moisture evaporation, and the output of the detection voltage also varies. Therefore, by providing the heat uniform layer 5 as in the first embodiment, the temperature distribution in the heater area HA shown in FIG. 8 can be reduced, and the humidity can be accurately measured.

That is, in the humidity sensor, as shown in FIG. 2, by providing the heat uniform layer 5 above the heater 3 via the insulating layer 12a, the difference between the temperature distribution and the set temperature in the humidity detection of the heater 3 can be reduced. The humidity sensor can be made smaller, and as a result, a highly accurate and highly reliable humidity sensor can be realized.

Further, in the humidity sensor, by making the size of the heat uniform layer 5 in plan view equal to or smaller than that of the heater 3, it is difficult to be influenced by the change of the ambient temperature and the power consumption of the heater 3 can be suppressed. ..

When the thermal conductivity of the fourth insulating film 12 including the insulating layer 12a between the heat uniform layer 5 and the heater 3 is higher than that of the heat uniform layer 5, the original heater temperature distribution tends to be close. Therefore, in order to further reduce the temperature distribution, it is desirable that the fourth insulating film 12 including the insulating layer 12a be formed of a material whose thermal conductivity is lower than that of the heat uniform layer 5. In particular, the temperature distribution can be further reduced by forming the fourth insulating film 12 such that the film thickness is thicker in the central portion of the heater and thinner toward the end portion of the heater. Further, in order to make the heat distribution (temperature distribution) on the heater 3 uniform, the heat uniform layer 5 may be thicker than the heater 3.

Further, as shown in FIG. 1, as the distance L between the heat uniform layer 5 and the semiconductor substrate 2 becomes shorter (shorter), the heat transfer to the semiconductor substrate 2 becomes larger, so that the width W of the heat uniform layer 5 becomes larger. Alternatively, it is desirable to separate (make longer) the width of the heater.

In the first embodiment, the humidity sensor has been described, but other sensors using a heater, such as an air flow rate sensor and an acceleration sensor, can improve the measurement accuracy by reducing the variation in the heater temperature.

<Example of Combining Humidity Sensor and Flow Rate Sensor of First Embodiment>
FIG. 10 is a schematic layout diagram showing a partially broken structure of a thermal air flow meter (sensor module) having the thermal fluid flow sensor according to the first embodiment of the present invention, and FIG. 11 is a BB line in FIG. FIG. 4 is a cross-sectional view of the sensor module taken along the line. Note that FIG. 10 shows an example of a sensor module attached to an intake passage of an internal combustion engine of an automobile or the like, and in order to make the structure of the sensor module easy to understand, a part of the module body (body) is made transparent. Showing.

As shown in FIGS. 10 and 11, the sensor module 20 is attached to the intake pipe 21, and has a support substrate 22 having wiring, the sensor chip 1, the air flow rate sensor 23, and adjustment parts (for example, a control circuit). (A chip, a microcomputer chip, a capacitor, etc.) 24 and a module main body 25 which is a body having the same. The sensor module 20 is composed of a module body 25 and a cover 25a.

The sensor chip 1, the air flow rate sensor 23, and the adjustment component 24 are mounted on the support substrate 22. Then, the sensor module 20 includes a sub-passage 26 for detecting the air flow rate by the air flow rate sensor 23, a detection unit 27 for detecting humidity and the like, and a control unit 29 which is a control circuit room in which the adjusting component 24 and the connector 30 are provided. They are separated and each element is electrically connected to the wiring of the support substrate 22 by wire bonding. The sensor chip 1 and the air flow rate sensor 23 send detection signals to the outside via the adjusting component 24 and the connector 30.

Further, the sensor chip 1 is covered with the protective material 31 shown in FIG. 11 so as not to corrode the electrodes 7a, 7b, 7c shown in FIG. 1 connected by wire bonding, and as shown in FIG. The intake air exchange port 28 is provided so that the air by the intake air 32 into the intake pipe 21 is appropriately exchanged.

In addition, the humidity detection on the surface of the sensor chip 1 affects the temperature distribution on the heat uniform layer 5 when a rapid air flow occurs, and the detection accuracy deteriorates. It is designed to be smaller than the shape of the passage.

Further, a part of the control circuit in the control unit 29 may be formed on the same support substrate 22 of the sensor chip 1. In that case, measure the humidity detection voltage when the relative humidity is changed at the same environmental temperature, create a map to calculate the water content from the humidity detection voltage, write it in the control circuit or microcomputer chip, and output it to the outside. To do.

(Embodiment 2)
<Structure of thermal resistance humidity sensor>
The thermal resistance-type humidity sensor according to the second embodiment is provided with a plurality of heaters as compared with the thermal resistance-type humidity sensor according to the first embodiment.

FIG. 12 is a plan view of an essential part of a sensor chip in the thermal resistance type humidity sensor according to the second embodiment of the present invention. As shown in FIG. 12, the sensor chip 41 includes a semiconductor substrate (supporting substrate) 42 made of single crystal silicon (Si), an insulating film (not shown) formed on the semiconductor substrate 42, and the above insulating film. The heater (first heater) 43 formed on the heater 43, the wirings 44a and 44b for supplying power to the heater 43, and the heat uniform layer 45 for averaging the temperature distribution of the layers on the heater 43. Further, in the sensor chip 41, the wiring 46 for preventing the heat uniform layer 45 from being charged up, the auxiliary heater (second heater) 47 formed so as to surround the heater 43, and the wiring 48 a for supplying power to the auxiliary heater 47. , 48b and electrodes 49a, 49b, 49c, 49d, 49e for connecting the wirings 44a, 44b, 46, 48a, 48b to the outside.

The heater 43, the uniform heat layer 45, and the auxiliary heater 47 are provided in the diaphragm 50, which is formed by removing the semiconductor substrate 42 and is an insulating film region above the cavity 42a shown in FIG. Further, the semiconductor substrate 42 is arranged at a position separated from the semiconductor substrate 42 by a predetermined distance, and is further insulated.

Here, FIG. 13 is a cross-sectional view of the structure taken along the line CC of FIG. As shown in FIG. 13, a first insulating film 51, a second insulating film 52, and a third insulating film 53 are formed on the semiconductor substrate 42. Further, a heater 43 and an auxiliary heater 47 are provided on the third insulating film 53, and wirings 44a, 44b, 48a, 48b shown in FIG. 12 for supplying power to the heater 43 and the auxiliary heater 47 are arranged. Then, the heat uniform layer 45 and the wiring 46 are formed on the heater 43 with the fourth insulating film 54 including the insulating layer 54a interposed therebetween.

Further, a fifth insulating film 55, a sixth insulating film 56, and a seventh insulating film 57 are stacked on the fourth insulating film 54, and a connecting portion 58 is formed on the seventh insulating film 57. The electrode 49c is formed via the electrode. Further, in order to prevent the corrosion of the electrode 49c, a protective film 59 is formed except a part thereof. The protective film 59 is preferably not placed on the heater 43 and the auxiliary heater 47 in order to stabilize the heater temperature, and the material thereof is, for example, a silicon oxide film, a silicon nitride film, or a polyimide film.

Further, as described above, the heater 43, the heat uniform layer 45, and the auxiliary heater 47 are arranged in the diaphragm 50 which is the region of the insulating film on the cavity 42a formed by removing the semiconductor substrate 42, and the semiconductor It is arranged at a distance from the substrate 42.

Next, the formed chip is fixed on the pedestal 60 with the adhesive 62, and the manufacturing of the sensor chip 41 is completed. The pedestal 60 is provided with a ventilation hole 61 so that the diaphragm 50 is not sealed, and the adhesive 62 is arranged so as not to block the ventilation hole 61. Further, although the ventilation hole 61 is formed in the lower surface in the second embodiment, it may be formed in the lateral direction of the pedestal 60 by a groove or the like and communicate with the outside.

Here, the structure of the main part of the humidity sensor of the second embodiment will be described. The auxiliary heater 47 is provided so as to surround the heater 43 at a position between the semiconductor substrate 42 and the heater 43 in plan view. Therefore, the temperature at the time of heating is lower than that of the heater 43.

Further, as shown in FIG. 12, the heat uniform layer 45 is arranged at a position inside the auxiliary heater 47 in plan view, and covers the heater 43 as shown in FIG. 13. That is, the heat uniform layer 45 does not extend over the heater 43 and the auxiliary heater 47 and does not cover them. In other words, the heat uniform layer 45 does not cover both the heater 43 and the auxiliary heater 47 in the connected layer state.

Further, the distance (L2) between the auxiliary heater 47 and the semiconductor substrate 42 in plan view is longer (L2>L1) than the distance (L1) between the heat uniform layer 45 and the auxiliary heater 47 in plan view.

The rest of the structure of the humidity sensor according to the second embodiment is similar to that of the humidity sensor according to the first embodiment, and a duplicate description thereof will be omitted.

<Effects of Humidity Sensor of Second Embodiment>
FIG. 14 is a diagram showing a temperature profile with respect to the distance from the center of the heater in the comparative example for each environmental temperature, and FIG. 15 is a diagram showing a temperature profile with respect to the distance from the center of the heater in the second embodiment of the present invention for each environmental temperature. .. 14 and 15 each show a temperature profile with the center of the heater in the line C-C of FIG. 12 as the reference.

As shown in FIG. 15, in the temperature profile of the second embodiment, the thermal uniformity of FIG. 13 is obtained regardless of whether the environmental temperature is 20° C. (K) or 80° C. (M). It can be seen that in the region where the single layer 45 is provided (first heater region HA1), the central portion of the heater is prevented from becoming high in temperature, and the heat distribution in the heater region is made uniform, as in the first embodiment. On the other hand, in the temperature profile of the comparative example shown in FIG. 14 in which the structure does not have the heat uniform layer, whether the environmental temperature is 25° C. (I) or the environmental temperature is 80° C. (J), It can be seen that in the heater area HA, the central portion of the heater has a high temperature, and the heat distribution in the heater area is not uniform.

Further, according to the temperature profile shown in FIG. 15 having the structure having the heat uniform layer 45 according to the second embodiment, the first heater for detecting the humidity by providing the auxiliary heater 47 and keeping the temperature higher than the ambient temperature. It is possible to reduce the influence on the heater area HA1. Further, even when an air flow occurs, the temperature change can be mitigated by the second heater area HA2, so that the humidity detection accuracy is maintained as compared with the structure of the comparative example having no heat uniform layer. I understand.

Regarding the change in the temperature distribution, the wider the second heater area HA2 and the higher the temperature of the auxiliary heater 47, the greater the effect of alleviating the temperature change. However, when the second heater area HA2 is large, or when the temperature of the auxiliary heater 47 is high, the power consumption of the auxiliary heater 47 increases. Therefore, considering the overall power consumption, the size of the second heater area HA2 is large. , And the temperature needs to be designed.

Here, the temperature when the heater 43 is heated is, for example, 500° C. or higher, but the temperature when the auxiliary heater 47 is heated is preferably around 300° C. at which the humidity detection voltage rises. Further, from the viewpoint of power consumption, it is desirable that the heat uniform layer 45 be arranged so as not to overlap the auxiliary heater 47 in plan view. That is, the heat uniform layer 45 does not straddle and cover both the heater 43 and the auxiliary heater 47. As an example, in the structure shown in FIG. 13, the heat uniform layer 45 covers only the heater 43 and does not cover the auxiliary heater 47. That is, the heat uniform layer 45 does not have to cover both the heater 43 and the auxiliary heater 47 in a connected layer state, and for example, the heat uniform layer 45 in a separated state (not connected state) is The heater 43 and the auxiliary heater 47 may be individually covered.

Further, as shown in FIG. 13, the distance L2 between the auxiliary heater 47 and the semiconductor substrate 42 is made larger than the distance L1 between the heat uniform layer 45 and the auxiliary heater 47 (L2>L1), so that the heat to the semiconductor substrate 42 is increased. It is possible to prevent transmission and improve the accuracy of humidity detection.

Further, for example, in the case of the structure in which the flow rate sensor and the humidity sensor shown in FIG. 10 are combined, the sensor chip 1 is connected to the intake pipe 21 by the intake replacement port 28, and the air in the intake pipe 21 constantly flows in and out. An air flow is generated on the sensor chip 1. That is, since the air flow is generated on the sensor chip 1, the temperature profile is likely to change under the influence of the air flow.

Therefore, also in the structure shown in FIG. 10, by providing the auxiliary heater (second heater) 47 as shown in FIGS. 12 and 13, it is possible to stabilize the temperature of the air in the intake pipe 21.

Other effects obtained by the humidity sensor according to the second embodiment are similar to those of the humidity sensor according to the first embodiment, and thus their duplicate description will be omitted.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are included. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described.

Further, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. .. Further, it is possible to add, delete, or replace another configuration with respect to a part of the configuration of each embodiment. It should be noted that each member and relative size described in the drawings are simplified and idealized in order to explain the present invention in an easy-to-understand manner, and have a more complicated shape in terms of mounting.

In the first and second embodiments described above, in the structure of the sensor chip of the humidity sensor, the case where the heat uniform layer is provided on the upper surface side of the heater has been described. However, the heat uniform layer is provided on the side opposite to the upper surface side of the heater. It may be provided at a position, that is, on the lower surface side of the heater. Even with the structure in which the heat uniform layer is provided on the lower surface side of the heater, the same effects as those of the first and second embodiments can be obtained.

Further, the support substrate is not limited to the semiconductor substrate, and may be a ceramic substrate or the like.

1, 41 Sensor chip 2, 42 Semiconductor substrate (support substrate)
2a, 42a Cavity 3, 43 Heater (first heater)
4a, 4b, 44a, 44b, 48a, 48b Wiring 5, 45 Heat uniform layer 6, 46 Wiring 7a, 7b, 7c, 49a, 49b, 49c, 49d, 49e Electrode 8, 50 Diaphragm 9, 51 First insulating film 10, 52 second insulating film 11, 53 third insulating film 12, 54 fourth insulating film 12a, 54a insulating layer 13, 55 fifth insulating film 14, 56 sixth insulating film 15, 57 seventh Insulating film 47 Auxiliary heater (second heater)

Claims (14)

A supporting substrate having a cavity,
A first heater disposed on the support substrate,
A heat uniform layer provided on the upper surface side or the lower surface side of the first heater and having a thermal conductivity equal to or higher than the thermal conductivity of the first heater;
An insulating layer disposed between the first heater and the heat uniform layer;
Have
The first heater and the heat uniform layer are disposed in a region of the insulating film on the cavity,
The heat uniform layer is arranged so as to overlap the first heater in a plan view, and the size of the heat uniform layer in a plan view is equal to or less than that of the first heater ,
A humidity sensor that measures humidity by using a change in voltage output from the first heater. The humidity sensor according to claim 1,
The humidity sensor, wherein the heat uniform layer is made of a metal film having a heat conductivity higher than that of the insulating layer. The humidity sensor according to claim 1,
The humidity sensor, wherein the heat uniform layer is made of the same material as the first heater. The humidity sensor according to claim 1,
The humidity sensor, wherein the thickness of the heat uniform layer is not less than the thickness of the first heater. The humidity sensor according to claim 1,
The humidity sensor, wherein the heat uniform layer is disposed in another insulating layer made of the same material as the insulating layer. The humidity sensor according to claim 1,
The heat uniform layer is a humidity sensor electrically connected to a ground electrode to which a ground potential is supplied. The humidity sensor according to claim 1,
The humidity sensor, wherein the distance between the support substrate and the heat uniform layer in plan view is longer than the width of the heat uniform layer in plan view. The humidity sensor according to claim 1,
A humidity sensor in which a second heater having a lower heating temperature than the first heater is provided between the support substrate and the first heater in a plan view. The humidity sensor according to claim 8 ,
The humidity sensor, wherein the heat uniform layer covers the first heater at a position inside the second heater in a plan view. The humidity sensor according to claim 8 ,
The humidity sensor, wherein the heat uniform layer does not extend over and cover the first heater and the second heater. The humidity sensor according to claim 8,
A humidity sensor in which the distance between the second heater and the support substrate in plan view is longer than the distance between the heat uniform layer and the second heater in plan view. The humidity sensor according to claim 1,
A humidity sensor in which the center of the heat uniform layer and the center of the first heater are aligned in a plan view. The humidity sensor according to claim 1,
The humidity sensor, wherein the heat uniform layer is made of a metal film having a heat conductivity higher than that of the first heater. A method for manufacturing a humidity sensor, which measures humidity using a change in voltage output from a heater,
(A) a step of providing an insulating film on a supporting substrate,
(B) a step of forming the heater made of a metal film and the wiring connected to the heater on the insulating film,
(C) a step of forming a heat uniform layer on the heater via an insulating layer and a wiring connected to the heat uniform layer,
(D) a step of forming another insulating film on the heat uniform layer,
(E) forming a cavity in a region of the support substrate below the heater,
Have
The heat uniform layer has a thermal conductivity equal to or higher than the thermal conductivity of the heater,
Place the front Kihi over data and the heat uniform layer in the region of the insulating film on the cavity,
In the step (c), the humidity sensor is arranged so that the heat uniform layer overlaps with the heater in a plan view, and the size of the heat uniform layer in a plan view is equal to or smaller than that of the heater. Manufacturing method.

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