JP6990165B2 - Thermal sensors and their manufacturing methods and semiconductor devices - Google Patents

Description

The present invention relates to a thermal sensor and a manufacturing technique thereof and a semiconductor device, and relates to, for example, a humidity sensor for measuring humidity and a manufacturing method thereof, and a technique applicable to a semiconductor device including the humidity sensor.

According to Japanese Patent Application Laid-Open No. 2010-133897 (Patent Document 1), the stress of the diaphragm is formed by forming an insulating film located below the finely processed heat-generating resistor from a laminated film of a compressive stress film and a tensile stress film. A technique relating to a flow sensor capable of suppressing imbalance and improving the measurement accuracy of gas flow rate is described.

Japanese Patent Application Laid-Open No. 2014-16177 (Patent Document 2) uses a thermal stress relaxation film having a higher thermal conductivity than an insulating film as a heater in order to prevent the occurrence of cracks due to thermal stress in a sensor that requires heating. The technique of contacting the part is described.

Japanese Unexamined Patent Publication No. 2010-133897 Japanese Unexamined Patent Publication No. 2014-16177

In recent years, in internal combustion engines such as automobiles, electronically controlled fuel injection devices have been provided in order to improve fuel efficiency. The fuel injection device incorporates various thermal sensors that detect the amount of intake air and the pressure and humidity of the intake air. As such a thermal sensor, there is a MEMS sensor manufactured by MEMS (Micro Electro Mechanical Systems) technology. This MEMS sensor has the advantages of being excellent in responsiveness, being able to be driven with low power consumption, and being able to further reduce costs.

In a thermal sensor composed of such a MEMS sensor, a physical quantity is measured by using heat. In particular, in a thermal sensor, resistance wiring is used to form a heater as a heating source by using resistance wiring, or to measure a physical quantity by using resistance change of resistance wiring.

Here, for example, the resistance wiring is covered with an insulating film, but according to the study of the present invention, depending on the type of the insulating film covering the resistance wiring, the linear expansion rate between the insulating film covering the resistance wiring and the resistance wiring From the difference, it was newly found that plastic deformation occurs due to the heat generated from the resistance wiring.

When the insulating film covering the resistance wiring is plastically deformed, the resistance wiring covered with the insulating film is bent, and the resistance of the resistance wiring changes with time. The change in the resistance of the resistance wiring due to the deflection leads to a decrease in the measurement accuracy of the physical quantity in the thermal sensor. Therefore, it is desired to suppress the change in resistance of the resistance wiring over time. In particular, considering that the deflection of the resistance wiring causes a change in the resistance of the resistance wiring over time, it is desired to take measures to reduce the plastic deformation of the insulating film that causes the deflection of the resistance wiring.

Other issues and novel features will become apparent from the description and accompanying drawings herein.

The thermal sensor in one embodiment has a resistance wiring including a first portion extending in a first direction and a second portion parallel to the first portion. At this time, the thermal sensor is formed between the first portion and the second portion, has a tensile stress, and has a stress adjusting film whose thickness in the film thickness direction is smaller than the thickness of the resistance wiring. Have.

According to one embodiment, the performance of the thermal sensor can be improved.

It is a schematic diagram which shows the sensor module which incorporated the thermal type humidity sensor in embodiment, and is the schematic diagram which shows the inside through the surface cover of the sensor module in embodiment. It is sectional drawing which cut at the line AA of FIG. It is a figure which shows the layout structure of the semiconductor chip which constitutes a thermal type humidity sensor. FIG. 3 is a cross-sectional view taken along the line AA of FIG. It is sectional drawing which enlarges and shows a part of the upper layer part formed on the diaphragm in the thermal type humidity sensor of a related art. It is a figure which shows typically the state which the bending occurs in the upper layer part. It is sectional drawing which shows the structure which embodied the countermeasure plan. It is sectional drawing which shows the improvement of the measure plan. It is sectional drawing which shows the partial structure of the thermal type humidity sensor in embodiment. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor in embodiment. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor following FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor following FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor following FIG. It is a schematic diagram which shows the upper layer part of the thermal type humidity sensor in the modification 1. It is a graph which shows the amount of change of a surface step before and after heating by a heater. It is a graph which shows the result of having measured the resistance value of a heater at a predetermined time time by passing an electric current through a heater in a state where a thermal humidity sensor (semiconductor chip) was heated to 500 degreeC. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor in the modification 1. FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor following FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor following FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor following FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor following FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor following FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor which follows | FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor which follows | FIG. It is sectional drawing which shows the manufacturing process of the thermal type humidity sensor which follows | FIG. It is a schematic diagram which shows the structure of the thermal type humidity sensor in the modification 2. It is a schematic diagram which shows the structure of the thermal type humidity sensor in the modification 3. It is a schematic diagram which shows the structure of the thermal type humidity sensor in the modification 4.

In all the drawings for explaining the embodiments, the same members are designated by the same reference numerals in principle, and the repeated description thereof will be omitted. In addition, in order to make the drawing easier to understand, hatching may be added even if it is a plan view.

<Sensor module configuration>
The sensor module (semiconductor device) in the present embodiment is a sensor module incorporating a thermal sensor. There are no restrictions on where the thermal sensor can be applied, but the thermal sensor can be incorporated into a sensor module together with various sensors, for example.

In the present embodiment, a humidity sensor will be described as an example as a thermal sensor incorporated in the sensor module. 1 and 2 are schematic views showing a sensor module incorporating a thermal humidity sensor according to the present embodiment. In particular, FIG. 1 is a schematic view showing the inside through the surface cover of the sensor module in the present embodiment, and FIG. 2 is a cross-sectional view taken along the line AA of FIG.

In FIG. 1, the sensor module 100 according to the present embodiment is mounted on an intake pipe 101 through which gas flows, and has a support substrate 102. The support board 102 is composed of, for example, a printed circuit board on which wiring is printed, and various types of components are mounted on the support board 102. Specifically, on the support substrate 102, for example, a semiconductor chip 103 having a flow sensor for measuring the flow rate of the gas flowing through the intake pipe 101 and a semiconductor having a thermal humidity sensor for measuring the humidity of the gas are formed. A chip 104 and a semiconductor chip 105 in which a flow sensor and a thermal humidity sensor are formed with a control circuit are mounted. The support board 102 configured in this way is connected to the connector 106.

The body 107 of the sensor module 100 has a surface cover and an inner wall, and the semiconductor chip 103 on which the flow sensor is formed and the semiconductor chip 105 on which the control circuit is formed are arranged in the internal space of the body by the surface cover and the inner wall. It is divided into a control space 107A and a detection space 107B in which the semiconductor chip 104 on which the thermal humidity sensor is formed is arranged.

Further, the body 107 of the sensor module 100 is provided with an auxiliary flow path 108, and a part of the semiconductor chip 103 on which the flow rate sensor is formed is in contact with the auxiliary flow path 108.

Further, the detection space 107B partitioned by the body 107 of the sensor module 100 communicates with the gas replacement port 109. The gas replacement port 109 is provided on the downstream side where the gas flows so as not to be affected by the gas flow. The opening area of the gas replacement port 109 is smaller than that of the subchannel 108, and is composed of a crank shape. In particular, if a gas with a rapid flow comes into contact with the thermal humidity sensor (semiconductor chip 104) arranged inside the detection space 107B, the temperature distribution of the thermal humidity sensor is adversely affected, and the thermal humidity sensor is detected. The accuracy is reduced. For this reason, a configuration is adopted in which the detection space 107B communicates with the inside of the intake pipe 101 via the gas replacement port 109 described above.

Next, as shown in FIG. 2, the body 107 of the sensor module 100 arranges the control space 107A in which the semiconductor chip 105 in which the control circuit is formed is arranged, and the semiconductor chip 104 in which the semiconductor chip 104 in which the thermal humidity sensor is formed is arranged. The detection space 107B is separated from the detection space 107B. The detection space 107B communicates with the gas replacement port 109.

In FIG. 2, for example, the semiconductor chip 104 on which the thermal humidity sensor is formed is electrically connected to the wiring formed on the surface of the support substrate 102 via the wire 110A. Similarly, for example, the semiconductor chip 105 on which the control circuit is formed is electrically connected to the wiring formed on the surface of the support substrate 102 via the wire 110B. At this time, the wire 110A and the wire 110B may be configured to be covered with the protective material 111 in order to protect them from corrosion. In FIG. 2, as an example, a configuration in which the wire 110A is covered with the protective material 111 is shown.

As described above, the sensor module 100 according to the present embodiment is configured. The sensor module 100 in the present embodiment is not limited to the above-described configuration, and may be configured to include, for example, another detection space in which the pressure sensor is arranged. That is, in the sensor module 100 in the present embodiment, a sensor module in which a flow rate sensor and a thermal type humidity sensor are combined is described, but the present invention is not limited to this, and for example, a pressure sensor or another gas sensor and a thermal type humidity sensor are described. It can also be a sensor module in combination with the above, or a sensor module of a single thermal humidity sensor.

<Operation of sensor module>
The sensor module 100 in the present embodiment is configured as described above, and its operation will be briefly described below.

First, in FIG. 1, the gas (for example, air) taken into the inside of the intake pipe 101 passes through the auxiliary flow path 108. At this time, the flow rate of the gas is measured by the flow rate sensor (semiconductor chip 103) provided in contact with the subflow path 108, and the electric signal associated with the gas flow rate is output from the flow rate sensor (semiconductor chip 103). Will be done. Further, the gas flows into the detection space 107B from the gas replacement port 109. As a result, the humidity of the gas is measured by the thermal humidity sensor (semiconductor chip 104) provided inside the detection space 107B, and the electric signal associated with the humidity of the gas is transmitted from the humidity sensor (semiconductor chip 104). It is output.

The electric signal output from the flow rate sensor (semiconductor chip 105) and the electric signal output from the thermal humidity sensor (semiconductor chip 104) are input to the semiconductor chip 105 in which the control circuit is formed. Then, the control circuit calculates the gas flow rate based on the electric signal associated with the gas flow rate, and the flow rate data indicating the gas flow rate is transmitted from the semiconductor chip 105 on which the control circuit is formed to the connector 106 via the connector 106. Is output to an external device. Similarly, the control circuit calculates the humidity of the gas based on the electrical signal associated with the humidity of the gas, and the humidity data indicating the humidity of the gas is obtained from the semiconductor chip 105 on which the control circuit is formed to the connector 106. It is output to an external device via. As described above, the sensor module 100 according to the present embodiment can be operated.

For example, by incorporating the sensor module 100 configured in this way into an internal combustion engine such as an automobile, the amount of intake air, the pressure and humidity of the intake air are detected, and the optimum amount of fuel is sprayed onto the internal combustion engine. , The fuel efficiency of the internal combustion engine can be improved.

<Structure of thermal humidity sensor>
Next, the thermal humidity sensor incorporated in the sensor module 100 will be described.

FIG. 3 is a schematic diagram showing the layout configuration of the semiconductor chip 104 constituting the thermal humidity sensor. In FIG. 3, the planar shape of the semiconductor chip 104 has a rectangular shape. For example, a quadrangular diaphragm 10 is formed on the back surface of the semiconductor chip 104. In FIG. 3, the diaphragm 10 is illustrated by a broken line.

Specifically, the planar shape of the diaphragm 10 is composed of, for example, a quadrangular shape having a side of 600 μm. The diaphragm 10 is defined as a thin portion having a thickness thinner than that of other semiconductor chips.

Subsequently, as shown in FIG. 3, a heater forming region is provided on the surface of the semiconductor chip 104 so as to be included in the diaphragm 10 in a plan view, and the heater 11 is formed in this heater forming region. ing. For example, the heater forming region has a rectangular shape of 90 μm square. The heater 11 formed in such a heater forming region is composed of, for example, a resistance wiring having a folded shape. Specifically, the heater 11 includes a first portion 11a extending in the y direction, a second portion 11b extending in the y direction in parallel with the first portion 11a, and a first portion 11a and a second portion 11b. It has a connection portion 11c and a connection portion 11c for connecting the above.

One end of the heater 11 is connected to the lead wiring 12a which is the lead wiring, while the other end of the heater 11 is connected to the lead wiring 12b which is the lead wiring. The lead wiring 12a is electrically connected to the electrode 13a that functions as an external connection terminal via the plug 14a. Similarly, the lead wiring 12b is electrically connected to the electrode 13b functioning as an external connection terminal via the plug 14b.

In the semiconductor chip 104 configured in this way, by passing a current between the electrodes 13a and 13b, a current can be passed through the heater 11 connecting the electrodes 13a and 13b. As a result, Joule heat can be generated from the resistance wiring constituting the heater 11. At this time, as shown in FIG. 3, in a plan view, the heater 11 is provided so as to be included in the diaphragm 10 which is a thin thin portion, so that the heating characteristics of the heater 11 can be improved. can. That is, it can be said that the diaphragm 10 is formed to improve the heating characteristics of the heater 11.

Next, FIG. 4 is a cross-sectional view taken along the line AA of FIG.

In FIG. 4, the semiconductor chip 104 constituting the thermal humidity sensor has roughly two portions, a lower layer portion 20a and an upper layer portion 20b.

As shown in FIG. 4, the lower layer portion 20a is composed of a semiconductor substrate 1 which is a support on which the opening 1a is formed and an insulating film 2 used as a mask when forming the opening 1a in the semiconductor substrate 1. Has been done. The semiconductor substrate 1 is made of, for example, single crystal silicon, and the insulating film 2 formed on the back surface of the semiconductor substrate 1 is made of, for example, a silicon oxide film.

Subsequently, as shown in FIG. 4, an upper layer portion 20b is provided on the lower layer portion 20a, and the upper layer portion 20b is composed of a plurality of films (laminated films).

Specifically, first, the upper layer portion 20b has an insulating film 3 formed on the semiconductor substrate 1 on which the opening 1a is formed. The insulating film 3 is formed of a silicon oxide film. The upper layer portion 20b has an insulating film 4 formed on the insulating film 3 and an insulating film 5 formed on the insulating film 4. At this time, the insulating film 4 is formed of a silicon nitride film, while the insulating film 5 is formed of a silicon oxide film.

Next, as shown in FIG. 4, the upper layer portion 20b has a heater 11 made of resistance wiring (heater wiring) formed on the insulating film 5. The heater 11 functions as a heat generation resistor of the humidity sensor. The heater 11 is made of a conductive material so that an electric current can flow. In particular, it is desirable to use a conductive material having a large Joule heat generated by the flow of an electric current, and further, in consideration of heat resistance, it is desirable that the heater 11 is made of, for example, a refractory metal material. Examples of the refractory metal material include molybdenum (Mo) and tungsten (W).

Subsequently, the upper layer portion 20b has an insulating film 6 formed on the insulating film 5 so as to cover the heater 11, an insulating film 7 formed on the insulating film 6, and an insulating film formed on the insulating film 7. Has 8 and. At this time, the insulating film 6 is formed of a silicon oxide film, while the insulating film 7 is formed of a silicon nitride film. Further, the insulating film 8 is formed of a silicon oxide film.

Here, as shown in FIG. 4, only the laminated film (insulating films 3 to 8 and the heater 11) constituting the upper layer portion 20b is formed on the opening 1a formed in the semiconductor substrate 1. From this, the thickness on the opening 1a formed in the semiconductor substrate 1 (thickness of only the upper layer 20b) is higher than the thickness of the portion other than the opening 1a (thickness of the lower layer 20a + the upper layer 20b). Also becomes thinner. As a result, in the semiconductor chip 104, the diaphragm 10 to be a thin-walled portion is formed by forming the opening 1a in the semiconductor substrate 1.

<Operation of thermal humidity sensor>
As described above, the semiconductor chip 104 constituting the thermal humidity sensor is configured, and the operation of the thermal humidity sensor will be described below with reference to the drawings.

First, the semiconductor chip 105 shown in FIG. 1 in which the control circuit is formed is electrically connected to the semiconductor chip 104 in which the thermal humidity sensor is formed. The control circuit formed on the semiconductor chip 105 has a CPU (central processing unit) and a memory, and is formed on the semiconductor chip 104 (thermal humidity sensor) shown in FIG. 3 under the control of the CPU. A voltage (potential difference) is applied between the electrode 13a and the electrode 13b. For example, the ground potential (0V) is applied to the electrode 13a, while the power supply potential (for example, 5V) is applied to the electrode 13b. As a result, a current flows through the heater 11 including the resistance wiring connected to the electrode 13a and the electrode 13b. As a result, Joule heat is generated in the heater 11, and the heater 11 generates heat. At this time, for example, the CPU maintains the temperature of the heater forming region in which the heater 11 is formed, for example, at about 500 ° C. by performing constant current control so that the current flowing through the heater 11 becomes constant.

Here, as shown in FIG. 4, when the heater 11 generates heat, the gas existing above and below the heater 11 is heated, and the water contained in the gas evaporates (vaporizes). At this time, a part of the heat generated from the heater 11 is consumed by the heat of vaporization required for evaporation of the water contained in the gas. That is, a part of the electric power supplied to the heater 11 is consumed by the heat of vaporization, and the electric power consumed by the heat of vaporization changes depending on the amount of water contained in the gas. For example, the more water contained in a gas, the greater the power required to evaporate the water. On the other hand, when the amount of water contained in the gas decreases, the electric power required for evaporation of the water decreases. This means that the power required to evaporate the water changes depending on the humidity of the gas. Here, since the CPU performs constant current control to keep the current flowing through the heater 11 constant, the change in the electric power consumed for the evaporation of water is the potential difference between the electrodes 13a and 13b. Appears as a change in. Therefore, the humidity of the gas can be measured by detecting the change in the potential difference between the electrodes 13a and 13b.

Specifically, the change in the potential difference between the electrodes 13a and 13b in the semiconductor chip 104 is monitored by the CPU included in the semiconductor chip 105. Then, when the CPU inputs an electric signal corresponding to the potential difference between the electrodes 13a and 13b from the thermal humidity sensor, for example, the voltage value of the electric signal and the humidity of the gas (humidity data) are associated in advance. Access the memory that stores the table and acquire the humidity (humidity data) of the gas corresponding to the voltage value of the electric signal input from the thermal humidity sensor. After that, the CPU outputs the humidity (humidity data) of the acquired gas to the outside. In this way, the humidity of the gas can be measured.

In this way, the thermal humidity sensor that measures absolute humidity using the heater 11 is, for example, a humidity sensor that uses a humidity sensitive film to measure relative humidity from changes in the resistance and capacitance values of the moisture sensitive film. In comparison, it has the advantage of high humidity detection sensitivity. This is because, for example, the moisture-sensitive film changes its resistance value and capacity value by adsorbing moisture, but the amount of moisture adsorbed is limited, and in a high humidity environment, the moisture adsorbed on the moisture-sensitive film This is because the amount is saturated and the resistance value and the capacitance value do not change according to the humidity. On the other hand, in the thermal humidity sensor, the humidity of the gas is measured by utilizing the fact that the potential difference between both ends of the heater 11 changes depending on the amount of heat required for evaporation of water, so that even in a high humidity state. Detection accuracy can be ensured. That is, since the thermal humidity sensor is not a humidity sensor that utilizes the adsorption of moisture by the moisture-sensitive film, the humidity detection sensitivity does not decrease due to the saturation of the moisture adsorption by the moisture-sensitive film. For this reason, the thermal humidity sensor has an advantage that the detection accuracy of the humidity of the gas is higher than that of the humidity sensor using the humidity sensitive film. Therefore, it can be said that the thermal humidity sensor is particularly excellent in detecting humidity in a high temperature and high humidity environment.

For example, in a thermal humidity sensor, when the temperature of the heater 11 is set to 500 ° C. or higher, the humidity detection sensitivity is good, and appropriate detection sensitivity is obtained not only for air but also for carbon monoxide (CO) and other gases. be able to. Further, in the thermal humidity sensor, it is possible to realize a humidity sensor that can handle various gases with high accuracy even at 600 ° C. or higher.

However, as a result of the study by the present inventor, it has become clear that there is room for improvement in the thermal humidity sensor due to the use of heat. Therefore, in the following, the room for improvement existing in the thermal humidity sensor will be described using related techniques.

<Examination of improvement>
The "related technology" referred to in the present specification is a technology having a problem newly found by the inventor, and is not a known conventional technology, but is intended as a prerequisite technology (unknown technology) of a new technical idea. It is a technique described in.

FIG. 5 is an enlarged cross-sectional view showing a part of the upper layer portion 20b formed on the diaphragm (not shown in FIG. 5) in the thermal humidity sensor of the related technology.

As shown in FIG. 5, the humidity sensor in the related art has an insulating film 3, an insulating film 4 formed on the insulating film 3, and an insulating film 5 formed on the insulating film 4. The humidity sensor in the related technology has a heater 11 on the insulating film 5. The heater 11 includes at least a first portion 11a and a second portion 11b adjacent to each other. The thermal humidity sensor in the related technology further includes an insulating film 6 formed so as to cover the heater 11, an insulating film 7 formed on the insulating film 6, and an insulating film formed on the insulating film 7. Has 8 and.

At this time, as shown in FIG. 5, in the thermal humidity sensor in the related technology, for example, the insulating film 6 is embedded between the first portion 11a and the second portion 11b constituting the heater 11. The insulating film 6 embedded between the first portion 11a and the second portion 11b constituting the heater 11 is made of, for example, a silicon oxide film.

Here, when the thermal humidity sensor in the related technology is operated, a current flows through the heater 11. As a result, Joule heat is generated in the heater 11, and the temperature of the heater 11 becomes high. At this time, in the thermal humidity sensor, the higher the set temperature of the heater 11, the higher the humidity detection sensitivity of the humidity sensor. This is because raising the temperature of the heater 11 means that the potential difference applied to both ends of the heater 11 becomes large, and the voltage change (voltage change corresponding to the amount of heat consumed for evaporation (vaporization) of the water contained in the gas). This is because ΔV) becomes large. For example, when the potential difference applied to both ends of the heater 11 is "2V" and the voltage change (ΔV) corresponding to the amount of heat consumed for evaporation of the water contained in the gas is 0.2V, the heater 11 When the potential difference applied to both ends of the gas is "3V", the voltage change (ΔV) corresponding to the amount of heat consumed for evaporation of the water contained in the gas is 0.3V (0.2V / 2V = 0). .3V / 3V). That is, when the potential difference applied to both ends of the heater 11 is "2V", the absolute value of the voltage signal to be detected is 0.2V, while when the potential difference applied to both ends of the heater 11 is "3V", it is detected. The absolute value of the voltage signal to be should be 0.3V. Then, for example, assuming that the background noise of the detection system is "0.01V", the S / N ratio (signal / noise ratio) when the potential difference applied to both ends of the heater 11 is "2V" is "0. 2V / 0.01V = 20 ”. On the other hand, when the potential difference applied to both ends of the heater 11 is "3V", the S / N ratio (signal / noise ratio) is "0.3V / 0.01V = 30". Therefore, when the potential difference applied to both ends of the heater 11 becomes large, the S / N ratio becomes large, which means that the detection sensitivity is improved when the potential difference applied to both ends of the heater 11 becomes large. From the above, in the thermal humidity sensor, the higher the set temperature of the heater 11, the higher the humidity detection sensitivity of the humidity sensor.

Therefore, for example, in the thermal humidity sensor in the related technology, the set temperature of the heater 11 is higher than that of the thermal sensor represented by other flow rate sensors. Specifically, in the thermal humidity sensor, the temperature of the heater 11 is set to about 300 ° C. to 600 ° C. In this case, there is room for improvement in the thermal humidity sensor in the related technology.

Specifically, as shown in FIG. 5, in the thermal humidity sensor in the related technology, an insulating film 6 made of a silicon oxide film is embedded between the first portion 11a and the second portion 11b constituting the heater 11. There is. At this time, the heater 11 is made of, for example, a refractory metal material typified by molybdenum (Mo) or tungsten (W), and for example, the linear expansion coefficient of molybdenum (Mo) is about 5.1 × 10. ^-6 / K. On the other hand, the linear expansion coefficient of silicon oxide constituting the insulating film 6 is about 0.7 × 10 ^-6 / K. Therefore, the linear expansion rate of the first portion 11a and the second portion 11b constituting the heater 11 and the linear expansion rate of the insulating film 6 embedded between the first portion 11a and the second portion 11b are different. It will be. The linear expansion coefficient of molybdenum (Mo) constituting the heater 11 is about 5.1 × ^10-6 / K, while the linear expansion coefficient of silicon oxide constituting the insulating film 6 is about 0.7 × 10 ⁻ . Considering that it is ⁶ / K, when the heater 11 is heated, thermal stress, which is a tensile stress, is applied to the first portion 11a and the second portion 11b constituting the heater 11. On the other hand, thermal stress, which is a compressive stress, is applied to the insulating film 6 (silicon oxide film) embedded in the first portion 11a and the second portion 11b.

Here, in the thermal humidity sensor in the related technology, since the temperature of the heater 11 becomes a high temperature of about 300 ° C. to 600 ° C., the insulating film 6 (particularly, the first portion 11a and the second portion 11b) covering the heater 11 is formed. The embedded insulating film 6) also becomes hot. The insulating film 6 is made of a silicon oxide film, and the silicon oxide film has a property of softening when a high temperature of about 300 ° C. to 600 ° C. is applied (glass transition). Therefore, when the heater 11 is heated, the insulating film 6 embedded between the first portion 11a and the second portion 11b constituting the heater 11 is softened with a thermal stress which is a compressive stress. As a result, for example, as shown in FIG. 6, the insulating film 6 embedded between the first portion 11a and the second portion 11b constituting the heater 11 is plastically deformed. In particular, the plastic deformation of the insulating film 6 embedded between the first portion 11a and the second portion 11b progresses over time. As a result, as shown in FIG. 6, bending occurs in the upper layer portion 20b composed of the laminated film of the insulating films 3 to 8. This means that the heater 11 embedded in the upper layer portion 20b also bends. The fact that the heater 11 is bent means that the resistance value of the heater 11 changes. In particular, the fact that the insulating film 6 embedded between the first portion 11a and the second portion 11b constituting the heater 11 undergoes plastic deformation over time means that the deflection of the heater 11 also changes over time. As a result, the resistance value of the heater 11 changes with time.

At this time, in the thermal humidity sensor in the related technology, constant current control is performed to keep the current flowing through the heater 11 constant, and the potential difference between both ends of the heater 11 fluctuates depending on the humidity of the gas. , Measuring the humidity of the gas. However, in constant current control, the fact that the resistance value of the heater 11 changes with time means that the potential difference between both ends of the heater 11 fluctuates even if the humidity of the gas is the same. This means that the thermal humidity sensor in the related technology has a reduced accuracy of detecting the humidity of the gas. That is, the fact that the resistance value of the heater 11 changes with time means that it becomes difficult to maintain the detection accuracy of the humidity of the gas for a long period of time. In other words, the fact that the resistance value of the heater 11 changes with time means that the long-term reliability of the thermal humidity sensor in the related technology cannot be ensured. As described above, in the thermal humidity sensor in the related technology in which the temperature of the heater 11 becomes high, the insulating film 6 sandwiched between the first portion 11a and the second portion 11b of the heater 11 undergoes plastic deformation. As a result, the resistance value of the heater 11 changes with time. As a result, there is room for improvement in the thermal humidity sensor in the related technology, which makes it difficult to secure the detection accuracy of the humidity of the gas over a long period of time.

<Countermeasure plan>
According to the mechanism described above, in order to ensure the detection accuracy of the humidity of the gas over a long period of time in the thermal humidity sensor, it is important to suppress the change with time of the resistance value of the heater 11. The cause of causing the resistance value of the heater 11 to change with time is that the insulating film 6 sandwiched between the first portion 11a and the second portion 11b of the heater 11 undergoes plastic deformation. This plastic deformation is caused by the property of softening when the temperature of the heater becomes high and the property of applying thermal stress which is a compressive stress due to the difference in linear expansion rate from the refractory metal material constituting the heater 11. Therefore, in order to ensure the detection accuracy of gas humidity over a long period of time in the thermal humidity sensor, the temperature of the heater 11 is used as the insulating film 6 embedded between the first portion 11a and the second portion 11b of the heater 11. However, it is considered that an insulating film that does not easily cause plastic deformation may be used even when the temperature becomes as high as 300 ° C to 600 ° C. That is, as a countermeasure, the insulating film 6 embedded between the first portion 11a and the second portion 11b of the heater 11 has a property that it is difficult to soften even when the temperature of the heater becomes high, and it is not a compressive stress. It is conceivable to use an insulating film having a property of applying thermal stress, which is a tensile stress, due to the difference in linear expansion rate from the refractory metal material constituting the heater 11.

FIG. 7 is a cross-sectional view showing a structure embodying the above-mentioned countermeasure plan. In FIG. 7, in the countermeasure plan, the insulating film 30 is formed so as to cover the heater 11. As a result, for example, an insulating film 30 is embedded between the first portion 11a and the second portion 11b constituting the heater 11 instead of the insulating film 6. Here, the insulating film 6 is a silicon oxide film, and is a film to which a property of softening and a thermal stress which becomes a compressive stress are applied when the temperature of the heater 11 becomes a high temperature of about 300 ° C. to 600 ° C. Therefore, when the insulating film 6 made of a silicon oxide film is embedded between the first portion 11a and the second portion 11b constituting the heater 11, the temperature of the heater 11 is 300 ° C. as in the related technique shown in FIG. Plastic deformation occurs at a high temperature of about 600 ° C. (see FIG. 6). On the other hand, in the countermeasure plan shown in FIG. 7, the insulating film 30 embedded between the first portion 11a and the second portion 11b constituting the heater 11 is made of, for example, a silicon nitride film. This silicon nitride film is difficult to soften even when the temperature of the heater 11 becomes a high temperature of about 300 ° C. to 600 ° C., and becomes a tensile stress due to the difference in linear expansion rate from the refractory metal material constituting the heater 11. A film to which thermal stress is applied. Therefore, in the countermeasure plan shown in FIG. 7, even when the temperature of the heater 11 becomes a high temperature of about 300 ° C. to 600 ° C., it is embedded between the first portion 11a and the second portion 11b. No plastic deformation occurs in the insulating film 30. As a result, in the countermeasure plan, it can be considered that the change with time of the resistance value of the heater 11 due to the plastic deformation can be suppressed.

However, in the above-mentioned countermeasure plan, although the plastic deformation of the insulating film 30 can be suppressed, the change in the resistance value of the heater 11 with time becomes large due to another factor. That is, as shown in FIG. 7, in the countermeasure plan, an integral insulating film 30 is formed so as to cover the entire heater 11. In other words, not only the insulating film 30 is formed so as to fill the gap between the first portion 11a and the second portion 11b constituting the heater 11, but also the upper portions of the first portion 11a and the second portion 11b are formed. The insulating film 30 is formed so as to cover it. In this case, when the temperature of the heater 11 becomes high, a large tensile stress is applied to the integral insulating film 30 as shown in FIG. 7. Then, the large tensile stress applied to the insulating film 30 causes warpage over the entire heater forming region in which the heater 11 is formed, which causes distortion in the heater 11. As a result, the resistance value of the heater 11 fluctuates due to the influence of distortion. Therefore, the countermeasure plan is insufficient from the viewpoint of suppressing the change in the resistance value of the heater 11 with time.

Regarding this point, as an improvement of the countermeasure plan, for example, as shown in FIG. 8, it is conceivable to form the insulating film 30 only in the gap between the first portion 11a and the second portion 11b constituting the heater 11. .. That is, as shown in FIG. 7, instead of forming an integral insulating film 30 so as to cover the entire heater 11, as shown in FIG. 8, the first portion 11a and the second portion 11b constituting the heater 11 are formed. The insulating film 30 is formed only in the gap between the two. As a result, the insulating film 30 embedded in the gap of the heater 11 is divided, so that the magnitude of the tensile stress due to the insulating film 30 can be reduced. As a result, in the improvement of the countermeasure plan shown in FIG. 8, it is possible to suppress the occurrence of warpage over the entire heater forming region in which the heater 11 is formed. However, even in the improvement of the countermeasure plan shown in FIG. 8, the insulating film 30 is embedded in the entire gap between the first portion 11a and the second portion 11b constituting the heater 11, which is caused by the insulating film 30. Due to the tensile stress, the first portion 11a and the second portion 11b constituting the heater 11 are distorted. The fact that the first portion 11a and the second portion 11b constituting the heater 11 are distorted means that the resistance value of the heater 11 fluctuates due to the influence of the strain. Therefore, it can be seen that the improvement of the countermeasure plan shown in FIG. 8 is also insufficient from the viewpoint of suppressing the change in the resistance value of the heater 11 with time. As described above, the insulating film 30 has a property that it is difficult to soften even when the temperature of the heater becomes high, and the tensile stress is obtained due to the difference in the linear expansion rate from the refractory metal material constituting the heater 11 instead of the compressive stress. It is said that the countermeasure plan using an insulating film having the property of applying thermal stress is an insufficient countermeasure from the viewpoint of suppressing the fluctuation of the resistance value of the heater 11 and ensuring the detection accuracy of the gas humidity for a long period of time. be able to.

Therefore, in the present embodiment, a device is provided for providing a thermal humidity sensor that suppresses fluctuations in the resistance value of the heater 11 and secures detection accuracy of gas humidity over a long period of time. Hereinafter, the technical idea in the present embodiment to which this device has been devised will be described.

<Structure of thermal humidity sensor in the embodiment>
FIG. 9 is a cross-sectional view showing a partial configuration of the thermal humidity sensor according to the present embodiment.

FIG. 9 shows a configuration corresponding to the upper layer portion 20b on the diaphragm 10 shown in FIG. 4 in the thermal humidity sensor of the present embodiment. As shown in FIG. 9, the thermal humidity sensor in the present embodiment includes an insulating film 3 formed on a diaphragm (not shown in FIG. 9), an insulating film 4 formed on the insulating film 3, and an insulating film 4 formed on the insulating film 3. It has an insulating film 5 formed on the insulating film 4. The thermal humidity sensor in the present embodiment has a heater 11 formed on the insulating film 5. The heater 11 is composed of folded resistance wiring (see FIG. 3), and has at least a first portion 11a and a second portion 11b arranged side by side so as to be separated from each other. A gap (space) is provided between the first portion 11a and the second portion 11b, and the gap is used in the concept of including the insulating film 30 (semi-insulating film and wide-gap semiconductor film). ) And the insulating film 6 are embedded. The insulating film 6 is also formed above the heater 11 so as to cover the heater 11. The insulating film 30 is a stress relaxation film that relaxes the stress that causes the heater 11 to bend.

Further, the thermal humidity sensor in the present embodiment has an insulating film 7 formed on the insulating film 6 and an insulating film 8 formed on the insulating film 7. Here, the insulating film 3 is made of a silicon oxide film, and the insulating film 4 is made of a silicon nitride film. Further, the insulating film 5 is formed of a silicon oxide film. Further, the insulating film 6 is also made of a silicon oxide film, while the insulating film 7 is made of a silicon nitride film. Further, the insulating film 8 is made of a silicon oxide film. On the other hand, the insulating film 30 is made of an aluminum nitride film or a silicon nitride film.

Here, the silicon oxide film is a film having compressive stress and is softer than the silicon nitride film. On the other hand, the aluminum nitride film is a film having tensile stress and is harder than the silicon oxide film. The "compressive stress" and "tensile stress" referred to here are defined based on the case of contact with silicon. That is, when the silicon oxide film is brought into contact with silicon (the substrate), compressive stress is applied to the silicon oxide film due to the difference between the linear expansion rate of the silicon oxide film and the linear expansion rate of silicon. On the other hand, when the aluminum nitride film is brought into contact with silicon (the substrate), tensile stress is applied to the aluminum nitride film due to the difference between the linear expansion rate of the aluminum nitride film and the linear expansion rate of silicon. Similarly, when a silicon nitride film is brought into contact with silicon (a substrate), tensile stress is applied to the silicon nitride film due to the difference between the linear expansion rate of the silicon nitride film and the linear expansion rate of silicon. Furthermore, when the silicon oxide film and the aluminum nitride film are brought into contact with each other, compressive stress is applied to the silicon oxide film, while tensile stress is applied to the aluminum nitride film. Similarly, when the silicon oxide film and the silicon nitride film are brought into contact with each other, compressive stress is applied to the silicon oxide film, while tensile stress is applied to the silicon nitride film.

In FIG. 9, a laminated film composed of an insulating film 3, an insulating film 4, and an insulating film 5 is formed on a diaphragm (not shown in FIG. 9) for the following reasons. That is, for example, when only the silicon oxide film is formed on the diaphragm, the silicon oxide film functions as a compressive stress film, so that a large thermal stress is applied to the diaphragm formed below the silicon oxide film. , This may damage the diaphragm. Therefore, as shown in FIG. 9, a laminated film composed of a silicon oxide film (insulating film 3), a silicon nitride film (insulating film 4), and a silicon oxide film (insulating film 5) is formed on the diaphragm. In this case, the silicon oxide film functions as a compressive stress film, while the silicon nitride film functions as a tensile stress film. From this, the thermal stress of the laminated film as a whole becomes small due to the cancellation of the compressive stress and the tensile stress. This means that the thermal stress applied to the diaphragm is reduced. As a result, damage to the diaphragm can be suppressed. That is, the technical significance of forming the laminated film composed of the insulating film 3, the insulating film 4, and the insulating film 5 on the diaphragm is to suppress the breakage of the diaphragm due to thermal stress. This makes it possible to improve the reliability of the thermal humidity sensor.

Next, in FIG. 9, the reason why the laminated film composed of the insulating film 6, the insulating film 7, and the insulating film 8 is formed on the heater 11 will be described. For example, the insulating film 6 is formed of a silicon oxide film, the insulating film 7 is formed of a silicon nitride film, and the insulating film 7 is formed of a silicon oxide film. Here, the silicon oxide film has a property of being softer than that of the silicon nitride film and has a property of being less likely to be cracked. On the other hand, the silicon nitride film has a property of being harder than the silicon oxide film, but has a property of being easily cracked because it is hard. Therefore, when the silicon oxide film alone is used as the insulating film covering the heater 11, the crack resistance is excellent, but the strength is weak because it is soft. On the other hand, when the silicon nitride film alone is used as the insulating film covering the heater 11, the strength can be ensured because it is hard, but the crack resistance is deteriorated. Therefore, by using a laminated film of a silicon oxide film and a silicon nitride film as an insulating film covering the heater 11, the advantage of the silicon oxide film having excellent crack resistance and the nitriding that the strength from an external impact can be secured. You can get the advantages of silicon film. That is, the technical significance of using a laminated film composed of the insulating film 6, the insulating film 7, and the insulating film 8 as the insulating film covering the heater 11 is to achieve both improvement of crack resistance and securing of strength. This can improve the reliability of the thermal humidity sensor.

Furthermore, the silicon nitride film is a dense film and functions as a barrier film for preventing the infiltration of water. Therefore, as shown in FIG. 9, by providing silicon nitride films (insulating film 4 and insulating film 7) above and below the heater 11 so as to sandwich the heater 11, it is possible to suppress the infiltration of water reaching the heater 11. As a result, it is possible to suppress the occurrence of corrosion due to moisture in the heater 11 made of a metal material. From this point of view, the reliability of the thermal humidity sensor can be improved.

Subsequently, as shown in FIG. 9, in the thermal humidity sensor of the present embodiment, there is a tensile stress in the gap (space) between the first portion 11a and the second portion 11b constituting the heater 11. Moreover, the insulating film 30 whose thickness in the film thickness direction is smaller than the thickness of the heater 11 is formed. In other words, in the thermal humidity sensor of the present embodiment, the linear expansion coefficient is 1.0 × 10 ^-6 / in the gap (space) between the first portion 11a and the second portion 11b constituting the heater 11. It can also be said that the insulating film 30 having a thickness of K or more and 9.0 × ^10-6 / K or less and having a thickness in the film thickness direction smaller than the thickness of the heater 11 is formed. In addition to the above-mentioned insulating film 30, an insulating film 6 having compressive stress is also embedded in the gap (space) between the first portion 11a and the second portion 11b constituting the heater 11.

At this time, the insulating film 30 is formed on the insulating film 5, and the insulating film 30 is in contact with the insulating film 5. Then, for example, the occupied volume of the insulating film 30 formed in the gap (space) between the first portion 11a and the second portion 11b constituting the heater 11 is 1/3 of the volume of this gap (space). That is all. Further, for example, as shown in FIG. 9, the width (x direction) L of the first portion 11a constituting the heater 11 is the width (x) of the gap (space) between the first portion 11a and the second portion 11b. Direction) It is larger than S.

Next, for example, as shown in FIG. 3, the thermal humidity sensor (semiconductor chip 104) has a heater forming region in which the heater 11 is formed and an outer region outside the heater forming region in a plan view. is doing. At this time, as shown in FIG. 9, the insulating film 30 is formed in the heater forming region.

As described above, the thermal humidity sensor according to the present embodiment is configured.

<Characteristics in the embodiment>
Subsequently, the feature points of the thermal humidity sensor in the present embodiment will be described.

The first characteristic point in the present embodiment has, for example, as shown in FIG. 9, a tensile stress in the gap (space) between the first portion 11a and the second portion 11b constituting the heater 11. Moreover, the insulating film 30 whose thickness in the film thickness direction is smaller than the thickness of the heater 11 and a part of the insulating film 6 having compressive stress are embedded. As a result, according to the thermal humidity sensor of the present embodiment, it is possible to suppress the change of the resistance value of the heater 11 with time, thereby ensuring the detection accuracy of the gas humidity of the thermal humidity sensor over a long period of time. be able to.

The reason for this will be explained below.

For example, as in the related technique described above, when only the silicon oxide film, which is the insulating film 6 having compressive stress, is embedded in the gap between the first portion 11a and the second portion 11b constituting the heater 11, a thermal formula is used. When the temperature of the heater 11 is set to a high temperature of about 300 ° C. to 600 ° C. in order to operate the humidity sensor, the silicon oxide film embedded in the gap between the first portion 11a and the second portion 11b also becomes high temperature. The silicon oxide film has a property of softening when a high temperature of about 300 ° C. to 600 ° C. is applied. Therefore, when the heater 11 is heated, the silicon oxide film embedded between the first portion 11a and the second portion 11b constituting the heater 11 is softened with a thermal stress which is a compressive stress. As a result, for example, as shown in FIG. 6, the silicon oxide film embedded between the first portion 11a and the second portion 11b constituting the heater 11 is plastically deformed. This causes the heater 11 to bend, as shown in FIG. The fact that the heater 11 is bent means that the resistance value of the heater 11 changes. Therefore, for example, in the configuration in which only the silicon oxide film having compressive stress is embedded in the gap between the first portion 11a and the second portion 11b as in the related technology, the silicon oxide film undergoes plastic deformation, resulting in a heater. The resistance value of 11 changes with time.

Therefore, for example, as in the countermeasures (including improvements) shown in FIGS. 7 and 8, a silicon nitride film having tensile stress is provided in the gap between the first portion 11a and the second portion 11b constituting the heater 11. By adopting a configuration in which only the heater 11 is embedded, it is possible to suppress the change over time in the resistance value of the heater 11 due to plastic deformation, but the first portion 11a and the second portion 11b constituting the heater 11 are distorted due to too strong tensile stress. do. As a result, the resistance value of the heater 11 changes with time. Therefore, either a configuration in which the silicon oxide film alone is embedded in the gap between the first portion 11a and the second portion 11b constituting the heater 11 (related technology) or a configuration in which the silicon nitride film alone is embedded (countermeasure plan). Even with the configuration, it is difficult to suppress the change over time in the resistance value of the heater 11.

Regarding this point, according to the first feature point in the present embodiment, for example, as shown in FIG. 9, in the gap (space) between the first portion 11a and the second portion 11b constituting the heater 11. An insulating film 30 having a tensile stress and having a thickness in the film thickness direction smaller than the thickness of the heater 11 and a part of the insulating film 6 having a compressive stress are embedded. In this configuration, when the temperature of the heater 11 is set to a high temperature of about 300 ° C. to 600 ° C., the silicon oxide film (insulating film 6) embedded in the gap softens and tries to plastically deform. An insulating film 30 that does not soften is also embedded. From this, since the size (interval) of the gap is fixed by the insulating film 30, even if the silicon oxide film (insulating film 6) embedded in a part of the gap is softened, it is plastically deformed. Is hindered. That is, when the first feature point in the present embodiment is adopted, the presence of the insulating film 30 embedded in the gap suppresses the plastic deformation of the silicon oxide film embedded in the gap together with the insulating film 30. .. Thereby, according to the first characteristic point in the present embodiment, it is possible to suppress the fluctuation of the resistance value of the heater 11 due to the plastic deformation of the silicon oxide film.

Further, according to the first characteristic point in the present embodiment, the insulating film 30 embedded in the gap has a tensile stress, while the silicon oxide film (insulating film 6) embedded in the gap has a compressive stress. Has. Therefore, since the thermal stress applied to the insulating film 3 embedded in the gap and the silicon oxide film (insulating film 6) has opposite characteristics, the insulating film 30 and the silicon oxide film (insulating film 6) embedded in the gap have opposite characteristics. The absolute value of the stress acting on the combined laminated film becomes smaller. As a result, the strain generated in each of the first portion 11a and the second portion 11b constituting the heater 11 is, for example, a single insulating film 30 having a tensile stress in the gap, as in the countermeasures shown in FIGS. 7 and 8. The distortion generated in the first portion 11a and the second portion 11b can be reduced as compared with the embedded configuration. This means that, according to the first characteristic point in the present embodiment, it is possible to suppress the change over time in the resistance value of the heater 11 due to the strain generated in the first portion 11a and the second portion 11b constituting the heater 11. do.

From the above, the thermal humidity sensor having the first characteristic point in the present embodiment is the thermal humidity sensor in the related technology and the thermal humidity in the countermeasure plan from the viewpoint of suppressing the time-dependent change of the resistance value of the heater 11. It can be seen that it has an advantage over the sensor. That is, by adopting the first characteristic point in the first embodiment, it is possible to suppress the change with time of the resistance value of the heater 11 in the thermal humidity sensor, which has been difficult to realize by the conventional technology. As a result, according to the thermal humidity sensor of the present embodiment, it is possible to secure the detection accuracy of the gas humidity over a long period of time. In other words, according to the present embodiment, the performance of the thermal humidity sensor can be improved.

Here, it is desirable that the occupied volume of the insulating film 30 embedded in the gap is 1/3 or more of the volume (volume) of the gap. This is because when the occupied volume of the insulating film 30 embedded in the gap is less than 1/3 of the volume of the gap, it is difficult for the insulating film 30 to fully exert the function of fixing the size (interval) of the gap. Because it becomes. That is, if the occupied volume of the insulating film 30 embedded in the gap is less than 1/3 of the volume of the gap, it becomes difficult to suppress the occurrence of plastic deformation due to the softening of the silicon oxide film having compressive stress.

It is desirable that the occupied volume of the insulating film 30 embedded in the gap is determined in relation to the silicon oxide film (insulating film 6) embedded in the gap. Specifically, the silicon oxide film (insulating film 6) embedded in the gap has compressive stress, while the insulating film 30 embedded in the gap has tensile stress. At this time, when the compressive stress applied to the silicon oxide film and the tensile stress applied to the insulating film 30 cancel each other out, the total thermal stress of the silicon oxide film (insulating film 6) embedded in the gap and the insulating film 30 is increased. Very small. In this case, distortion is less likely to occur in the first portion 11a and the second portion 11b constituting the heater 11, whereby the change in the resistance value of the heater 11 with time can be effectively suppressed. Therefore, on the premise that the occupied volume of the insulating film 30 embedded in the gap is 1/3 or more of the volume (volume) of the gap, the insulating film 30 is added to the silicon oxide film (insulating film 6) embedded in the gap. It is desirable to determine to have a tensile stress of a magnitude that cancels the compressive stress. Furthermore, the linear expansion coefficient of the insulating film 30 is close to the linear expansion coefficient of the metal material constituting the heater 11 from the viewpoint of not distorting the first portion 11a and the second portion 11b constituting the heater 11. desirable.

The insulating film 30 can be made of, for example, an aluminum nitride film or a silicon nitride film. Here, for example, when the insulating film 30 is made of an aluminum nitride film, the aluminum nitride film has a property of high thermal conductivity, so that the variation in the temperature distribution in the heater forming region where the heater 11 is formed is suppressed. can do. For example, even when there is a temperature difference between the first portion 11a and the second portion 11b constituting the heater 11, it is embedded in the gap between the first portion 11a and the second portion 11b. The aluminum nitride film (insulating film 30) having high thermal conductivity alleviates the temperature difference between the first portion 11a and the second portion 11b. As a result, the temperature distribution in the heater forming region where the heater 11 is formed can be made uniform. This means that the voltage variation due to the evaporation of water from the gas is reduced, and thereby, according to the thermal humidity sensor of the present embodiment, the humidity measurement accuracy can be improved. On the other hand, when the insulating film 30 is composed of a silicon nitride film, silicon nitride is frequently used in silicon device manufacturing technology and is a material having a high affinity with silicon. Therefore, it is a silicon device. The advantage is that it is easy to apply to the sensor.

Next, the second characteristic point in the present embodiment is that, for example, as shown in FIG. 9, the insulating film 30 is formed only in the heater forming region. This is due to the following reasons. That is, for example, an aluminum nitride film is used as the insulating film 30, and as described above, this aluminum nitride film has a property of having high thermal conductivity. Therefore, for example, when the insulating film 30 is formed not only in the heater forming region but also in the outer region of the heater forming region, the heat generated by the heater 11 is generated outside the heater forming region by the aluminum nitride film having high thermal conductivity. It easily escapes to the area. This means that the electric power for raising the heater forming region to a predetermined temperature becomes large. That is, if the insulating film 30 is formed not only in the heater forming region but also in the outer region of the heater forming region, the power consumption efficiency is lowered and the power consumption of the thermal humidity sensor becomes larger than necessary. Regarding this point, according to the second characteristic point in the present embodiment in which the insulating film 30 is formed only in the heater forming region, the thermal humidity sensor is low while ensuring the detection accuracy of the gas humidity over a long period of time. The advantage of being able to increase power consumption can be obtained.

<Manufacturing method of thermal humidity sensor in the embodiment>
Subsequently, the method of manufacturing the thermal humidity sensor according to the present embodiment will be described with reference to the drawings. First, as shown in FIG. 10, a laminated film composed of the insulating film 3, the insulating film 4, and the insulating film 5 is formed. At this time, the insulating film 3 is formed of, for example, a silicon oxide film, and can be formed, for example, by using a CVD (Chemical Vapor Deposition) method. Further, the insulating film 4 is formed of, for example, a silicon nitride film, and a CVD method can be used, for example, and the insulating film 5 is formed of, for example, a silicon oxide film, for example, a CVD method can be used. It can be formed by use. After that, a metal film made of a refractory metal material typified by, for example, molybdenum (Mo) or tungsten is formed on the insulating film 5. This metal film can be formed, for example, by using a sputtering method. Then, by using the photolithography technique and the etching technique, the metal film is patterned to form the heater 11 made of resistance wiring. The heater 11 is composed of a resistance wiring processed into a folded shape, and at least a first portion 11a extending in the first direction and a second portion extending in the first direction in parallel with the first portion 11a. Includes 11b. At this time, a gap (space) is formed between the first portion 11a and the second portion 11b.

Next, as shown in FIG. 11, the insulating film 30 is formed on the insulating film 5 so as to cover the heater 11. The insulating film 30 is formed of, for example, an aluminum nitride film or a silicon nitride film. The aluminum nitride film is formed, for example, by using a sputtering method. On the other hand, the silicon nitride film can be formed, for example, by using a CVD method. Here, the insulating film 30 is formed in the gap between the first portion 11a and the second portion 11b constituting the heater 11, and is also formed on the upper surface of the first portion 11a and the upper surface of the second portion 11b. .. The film thickness of the insulating film 50 is smaller than the film thickness of the heater 11.

Subsequently, as shown in FIG. 12, the insulating film 30 is patterned by using a photolithography technique and an etching technique. The patterning of the insulating film 30 is performed so that the insulating film 30 remains only in the gap between the first portion 11a and the second portion 11b constituting the heater 11.

Next, as shown in FIG. 13, the insulating film 6 is formed on the insulating film 5 including the heater 11 and the insulating film 30. The insulating film 6 is formed of, for example, a silicon oxide film, and can be formed, for example, by using a CVD method. At this time, a part of the insulating film 6 is embedded in the gap between the first portion 11a and the second portion 11b constituting the heater 11. As a result, the insulating film 30 and the insulating film 6 are embedded in the gap between the first portion 11a and the second portion 11b. Specifically, an aluminum nitride film and a silicon oxide film are embedded in the gap.

Subsequent steps will be omitted. As described above, the thermal humidity sensor according to the present embodiment can be manufactured.

<Modification 1>
Next, a modification 1 in the embodiment will be described.

<< Configuration of thermal humidity sensor >>
FIG. 14 is a schematic view showing a part (upper layer portion) of the thermal humidity sensor in the present modification 1.

Since the configuration of the thermal humidity sensor in the present modification 1 shown in FIG. 14 has almost the same configuration as the configuration of the thermal humidity sensor in the embodiment shown in FIG. 9, the differences will be mainly described. do. In FIG. 14, the thermal humidity sensor in the first modification has an insulating film 30 that covers the heater 11. In particular, in the present modification 1, not only the insulating film 30 is formed in the gap between the first portion 11a and the second portion 11b constituting the heater 11, but also the insulating film 30 is formed on the first portion 11a and the second portion 11b. Also, the insulating film 30 is formed. That is, the insulating film 30 in the present modification 1 is formed as an integral film having an uneven shape according to the uneven shape of the heater 11. Also in the thermal type humidity sensor in the present modification 1 configured as described above, the first embodiment in which the insulating film 30 (film having tensile stress) and the insulating film 6 (film having compressive stress) are provided in the gap. One feature point is adopted. Therefore, the thermal humidity sensor in the first modification can also suppress the change over time in the resistance value of the heater 11 as in the thermal humidity sensor in the embodiment.

Here, the insulating film 30 in the present modification 1 is formed of an integral film having an uneven shape according to the uneven shape of the heater 11, but unlike the countermeasure plan shown in FIG. 7, for example, the heater It is a film that reflects the uneven shape of 11. Therefore, as shown in FIG. 14, for example, the portion of the insulating film 30 formed on the first portion 11a and the portion of the insulating film 30 formed on the second portion 11b are separated from each other. , The tensile stress is dispersed. Therefore, even if the insulating film 30 in the present modification 1 is formed, the tensile stress of the insulating film 30 does not become large enough to cause warpage, unlike the countermeasure plan shown in FIG. 7. Therefore, the thermal humidity sensor (see FIG. 14) in the first modification can suppress the time-dependent change of the resistance value of the heater 11 as in the thermal humidity sensor (see FIG. 9) in the embodiment. This point will be described below.

<< Effect in Modification 1 >>
FIG. 15 is a graph showing the amount of change in surface level difference before and after heating by the heater.

Here, the surface step indicates a step on the surface of the upper layer portion on the diaphragm. Then, in the present modification 1, the amount of change before heating by the heater 11 and after heating by the heater 11 (at 500 ° C. for 1000 hours) is measured by using a stylus type step meter.

In FIG. 15, the horizontal axis shows the distance from the center of the heater 11, and the vertical axis shows the amount of change in the surface step before and after heating. The graph (1) shows the measurement result after heating in the present modification 1, while the graph (2) shows the measurement result after heating in the related technique shown in FIG. The heater forming region is in the range of ± 45 μm in the center.

Focusing on the graph (2) of FIG. 15, it can be seen that in the related technique, the surface is deformed downward from the outer region (about ± 100 μm) of the heater forming region toward the center. Specifically, it can be seen that a change of about −0.13 μm occurs at the center of the heater 11. This means that in the thermal humidity sensor in the related technology, the central part of the heater forming region is plastically deformed. On the other hand, paying attention to the graph (1) in FIG. 15, it can be seen that in the present modification 1, there is almost no change in the surface step even after heating. From this result, it is confirmed that the thermal humidity sensor in the first modification suppresses the plastic deformation of the film.

FIG. 16 is a graph showing the results of measuring the resistance value of the heater 11 (acceleration test) by passing a current through the heater 11 in a state where the thermal humidity sensor (semiconductor chip) is heated to 500 ° C. Is. In FIG. 16, the horizontal axis represents the heating time (energization time) (hours), and the vertical axis represents the heater resistance change rate (%). The graph (1) shows the measurement results in the present modification 1, while the graph (2) shows the measurement results in the related technique shown in FIG.

Focusing on the graph (2) of FIG. 16, in the related technology, a change (rate of change) in the resistance value of 0.1% or more in a heating time of several hours and about 0.4% in a heating time of 1000 hours can be seen. You can see that. The amount of change in the resistance value of the heater 11 is about 20 g / m ² when converted into an error in absolute humidity, and the humidity at room temperature differs by about 10%.

On the other hand, focusing on the graph (1) of FIG. 16, in the present modification 1, the change is about 0.02% at the initial stage of the heating time, but the change in the resistance value of the heater 11 is changed even if the heating time is up to 1000 hours. The rate is about 0.03%, and it can be seen that the change in the resistance value of the heater with time is suppressed.

From the results of FIGS. 15 and 16, it can be seen that the change in the resistance value of the heater is largely related to the plastic deformation in the heater forming region. That is, when the heater 11 is composed of molybdenum (Mo), its linear expansion coefficient is about 5.1 × ^10-6 / K. Further, a silicon oxide film is embedded in the gap between the first portion 11a and the second portion 11b constituting the heater 11, and the linear expansion coefficient thereof is about 0.7 × 10 ^-6 / K. be. Due to such a difference in linear expansion coefficient, in the related technique, when heated for a long time, plastic deformation due to thermal stress occurs in the silicon oxide film. As a result, in the related technology, the heater 11 itself is also deformed, and the resistance value of the heater 11 changes significantly.

On the other hand, in the present modification 1, not only the silicon oxide film but also the linear expansion coefficient is 4.5 × 10 ^-6 / in the gap between the first portion 11a and the second portion 11b constituting the heater 11. An aluminum nitride film of K is embedded. This averages the linear expansion coefficients of the material embedded in the gap. As a result, the stress dispersion effect can be obtained, so that the plastic deformation of the silicon oxide film is suppressed. Therefore, since the change in the resistance value of the heater 11 with time due to the plastic deformation of the silicon oxide film is suppressed, the long-term reliability of the thermal humidity sensor can be ensured.

<< Manufacturing method of thermal humidity sensor >>
Next, a method of manufacturing the thermal humidity sensor in the first modification will be described.

First, as shown in FIG. 17, the semiconductor substrate 1 is prepared. As the semiconductor substrate 1, for example, a single crystal silicon substrate (silicon wafer) can be used. The single crystal silicon substrate is made of, for example, silicon (Si) having a crystal orientation of <100>.

Subsequently, as shown in FIG. 18, a three-layer insulating film is formed on the semiconductor substrate 1. Specifically, an insulating film 3 made of a silicon oxide film is formed on the semiconductor substrate 1. For example, the insulating film 3 can be formed by thermally oxidizing the semiconductor substrate 1. For example, the insulating film 3 made of a silicon oxide film can be formed by introducing oxygen or steam into a thermal oxidation furnace and applying heat of 1000 ° C. or higher. The silicon oxide film formed by the thermal oxidation method becomes a film having compressive stress. In this step, the insulating film 2 made of a silicon oxide film is formed not only on the upper surface of the semiconductor substrate 1 but also on the lower surface of the semiconductor substrate 1. However, the insulating film 3 formed on the upper surface of the semiconductor substrate 1 and the insulating film 2 formed on the lower surface of the semiconductor substrate 1 can be formed by different steps. After that, the insulating film 4 is formed on the insulating film 3. The insulating film 4 is made of a silicon nitride film and can be formed, for example, by using a CVD (Chemical Vapor Deposition) method. When formed by the CVD method, the silicon nitride film is a film having tensile stress. Then, the insulating film 5 is formed on the insulating film 4. The insulating film 5 is made of a silicon oxide film and can be formed, for example, by using a CVD method. The silicon oxide film formed by the CVD method becomes a film having compressive stress.

By laminating the film having compressive stress and the film having tensile stress in this way, as a result of reducing the film stress, it is possible to prevent an undesired stress from being applied to the humidity sensor itself.

In this modification, a configuration in which three layers of insulating films (insulating film 3, insulating film 4, and insulating film 5) are laminated has been described, but the present invention is not limited to this configuration, and a silicon nitride film and a silicon oxide film are added. It is also good. Further, when the three-layer insulating film is formed, the film stress can be stabilized by, for example, performing a heat treatment at 1000 ° C. in a nitrogen atmosphere.

Next, the surface of the insulating film 5 is modified by slightly etching the surface of the insulating film 5 made of the silicon oxide film. Specifically, for example, the surface of the insulating film 5 is etched by about 15 nm by sputtering etching using argon gas (Ar gas). After that, as shown in FIG. 19, a metal film (conductive film) 15 is formed on the insulating film 5 whose surface has been modified. For example, a refractory metal film is formed on the insulating film 5 by using a sputtering method. Here, a molybdenum film (Mo film) is formed at 160 nm as the refractory metal film. A tungsten film (W film) can also be used instead of the molybdenum film.

Subsequently, as shown in FIG. 20, the metal film 15 is patterned. Specifically, a photoresist film (not shown) is applied onto the metal film 15, and then the photoresist film is exposed and developed to pattern the photoresist film. Then, the metal film 15 is dry-etched using the patterned photoresist film as a mask. As a result, the metal film 15 can be patterned to form the heater 11 and the lead wiring (lead wiring 12a and lead wiring 12b shown in FIG. 3) made of the metal film 15. Then, the patterned photoresist film is removed.

In this way, the heater 11 and the lead wirings 12a and 12b are formed in the same layer. Forming in the same layer means forming in the same process using the same material.

In order to improve heat resistance, after forming the metal film 15 made of molybdenum film, heat treatment is performed in a nitrogen atmosphere at a heating temperature of 500 ° C. or higher, preferably 1000 ° C., which is the heating temperature when using the thermal humidity sensor. As a result, the grain growth of the metal film 15 can be promoted, and the fluctuation of the resistance value of the heater can be suppressed even when the heater is heated for a long time. Here, the linear expansion coefficient of the molybdenum film (metal film 15) is 5.1 × ^10-6 / K, which is larger than that of the silicon oxide film of about 0.7 × ^10-6 / K. The molybdenum film is a film having tensile stress.

Next, as shown in FIG. 21, an insulating film 30 that functions as a stress adjusting film is formed so as to cover the heater 11. For example, the insulating film 30 is made of an aluminum nitride film and can be formed by using, for example, a sputtering method. At this time, the film thickness of the insulating film 30 made of the aluminum nitride film is 150 nm, which is thinner than the film thickness of the heater 11 made of the molybdenum film. Therefore, the insulating film 30 is formed as an integral film having an uneven shape according to the uneven shape of the heater 11. Since the linear expansion coefficient of the aluminum nitride film is 4.5 × 10 ^-6 / K, which is almost equal to the linear expansion coefficient of the molybdenum film, the film has tensile stress. Here, the aluminum nitride film has a property of having high thermal conductivity. Therefore, for example, if the insulating film 30 is still formed not only in the heater forming region but also in the outer region of the heater forming region, the heat generated by the heater 11 is generated by the aluminum nitride film having high thermal conductivity. It easily escapes to the outer region of the forming region. This means that the electric power for raising the heater forming region to a predetermined temperature becomes large. That is, if the insulating film 30 is formed not only in the heater forming region but also in the outer region of the heater forming region, the power consumption efficiency is lowered and the power consumption of the thermal humidity sensor becomes larger than necessary.

Therefore, as shown in FIG. 22, the photoresist film is used as a mask, and the insulating film 30 is patterned so as to remain only in the heater forming region. As a result, even in the present modification 1, the insulating film 30 can be formed only in the heater forming region.

In order to stabilize the insulating film 30 that functions as a stress adjusting film, a heat treatment of 500 ° C. or higher, preferably 1000 ° C., which is the heating temperature when using the thermal humidity sensor, is performed in the patterning step of the insulating film 30. It is desirable to do it either before or after.

Subsequently, as shown in FIG. 23, a three-layer insulating film is formed over the insulating film 30 and the insulating film 5 covering the heater 11. Specifically, first, the insulating film 6 is formed over the insulating film 30 and the insulating film 5 that cover the heater 11. The insulating film 6 is made of, for example, a silicon oxide film, and can be formed, for example, by using a CVD method. The film thickness of the insulating film 6 is, for example, about 600 nm. At this time, a part of the insulating film 6 is embedded in the gap of the heater 11. As a result, the insulating film 30 and the insulating film 6 are embedded in the gap of the heater 11. Specifically, an aluminum nitride film and a silicon oxide film are embedded in the gap.

Then, for example, the surface of the insulating film 6 is flattened by using a CMP (Chemical Mechanical Polishing) method. Then, the insulating film 7 is formed on the flattened insulating film 6. The insulating film 7 is formed of a silicon nitride film, and can be formed, for example, by using a CVD method. Next, the insulating film 8 is formed on the insulating film 7. The insulating film 8 is made of a silicon oxide film and can be formed, for example, by using a CVD method.

By flattening the surface of the insulating film 6 made of the silicon oxide film in this way, the insulating film 7 and the insulating film 8 formed on the insulating film 6 are formed as a flat laminated film. As a result, it is possible to suppress the application of undesired stress to the thermal humidity sensor itself.

In order to adjust the stress of each of the insulating films 6 to 8, heat treatment can be performed after forming each of the insulating films 6 to 8. Further, the insulating film 4 made of a silicon nitride film and the insulating film 7 made of a silicon nitride film limit the insulating film 30 covering the heater 11 so as not to expand and contract to a yield state due to thermal stress when the heater 11 generates heat. It also has a function.

Here, for example, as shown in FIG. 23, in the present modification 1, the insulating film 7 made of a silicon nitride film is formed above the insulating film 30, has tensile stress, and has a flat surface. It is a thin film. As a result, for example, the thermal stress applied to the corner portion of the insulating film 30 covering the heater 11 is relaxed by the tensile stress provided in the insulating film 7 made of the silicon nitride film. This means that it is possible to suppress the generation of cracks in the corners of the insulating film 30 that covers the heater 11. That is, in the present modification 1, the insulating film 7 made of a silicon nitride film also has a technical significance of suppressing cracks generated in the corners of the insulating film 30 formed so as to cover the heater 11. Will be there.

Next, for example, referring to FIGS. 3 and 23, an electrode 13a electrically connected to the lead wiring 12a via the plug 14a and an electrode electrically connected to the lead wiring 12b via the plug 14b. The forming step with 13b will be described. Here, in the following, the reference numerals shown in FIG. 3, such as lead wiring (12a, 12b), are described by (reference numerals).

First, in FIG. 23, the insulating films 6 to 8 are formed so as to cover the heater 11, but the heater 11 and the lead wirings (12a, 12b) are formed in the same layer. Therefore, the insulating films 6 to 8 are also formed on the lead wirings (12a, 12b).

On the premise of this, first, a photoresist film is applied on the insulating film 8, and then the photoresist film is exposed and developed to form a photoresist film that opens a contact hole forming region (). Patterning of photoresist film). Then, using the patterned photoresist film as a mask, the insulating film 8, the insulating film 7, and the insulating film 6 are sequentially dry-etched to form contact holes reaching each of the lead wirings (12a, 12b). The surface of the lead wiring (12a, 12b) is exposed at the bottom of these contact holes. Then, the patterned photoresist film is removed.

Subsequently, the surface of the insulating film 8 and the surface of the lead wiring (12a, 12b) exposed from the contact hole are slightly etched to modify these surfaces. Specifically, for example, about 15 nm is etched by sputter etching using argon gas (Ar gas).

After that, electrodes (13a, 13b) electrically connected to the lead wiring (12a, 12b) are formed. Specifically, first, a metal film (conductive film) is formed on the insulating film 8 including the inside of the contact hole. For example, a barrier metal film is formed on the insulating film 8 including the inside of the contact hole by using a sputtering method, and a main metal film is formed on the barrier metal film. Here, for example, a titanium film (Ti film) is formed at 20 nm to 200 nm as a barrier metal film, and then an aluminum film (Al film) is formed as a main metal film with a thickness thicker than that of the barrier metal film. As a result, the inside of the contact hole is embedded by the barrier metal film and the main metal film to form plugs (14a, 14b).

As the barrier metal film, for example, a titanium nitride film (TiN film) or a tungsten nitride film (TiW film) can be used in addition to the titanium film, and these laminated films can be used as the barrier metal film. You can also. On the other hand, the main metal film is not limited to the aluminum film, and for example, an aluminum alloy film containing aluminum (Al) as a main component can be used.

Next, a photoresist film is applied on the main metal film, and the photoresist film is exposed and developed to cover the electrode forming region forming the electrodes (13a, 13b). Pattern the film. Then, the electrodes (13a, 13b) are formed by dry etching the main metal film and the barrier metal film using the patterned photoresist film as a mask. As a result, the electrode (13a) is electrically connected to the lead wiring (12a) via the plug (14a) in the contact hole. Similarly, the electrode (13b) is electrically connected to the lead wiring (12b) via a plug (14b) in the contact hole. After this, the patterned photoresist film is removed.

Subsequently, as shown in FIG. 24, the insulating film 2 made of the silicon oxide film formed on the back surface of the semiconductor substrate 1 is patterned by using the photolithography technique and the etching technique. The patterning of the insulating film 2 is performed so as to open the diaphragm forming region. Then, as shown in FIG. 25, a diaphragm (thin wall portion) 10 is formed on the semiconductor substrate 1 by wet-etching the semiconductor substrate 1 with the patterned insulating film 2 as a mask until the insulating film 3 is exposed. For example, wet etching is performed using a KOH (potassium hydroxide) solution or a TMAH (tetramethylamide) solution. However, the diaphragm 10 can be formed on the semiconductor substrate 1 not only by wet etching but also by dry etching using, for example, a fluorine-based gas.

Here, the insulating film 2 made of a silicon oxide film formed on the back surface of the semiconductor substrate 1 is used as a hard mask, but the present invention is not limited to this, and for example, a laminated film in which another film is laminated on the insulating film 2. (For example, a laminated film of a silicon oxide film and a silicon nitride film) can also be used as a hard mask. Further, after the processing on the upper surface side of the semiconductor substrate 1 is completed (for example, after forming the electrodes (13a, 13b)), a separate insulating film is formed on the back surface of the semiconductor substrate 1 and this insulating film is used as a mask. You can also do it.

After forming the diaphragm 10 on the semiconductor substrate 1, a protective insulating film is formed so as to cover the insulating film 8 and the electrodes (13a, 13b), and the protective insulating film formed on the electrodes (13a, 13b) is formed. By forming the opening, it is also possible to form a pad in which a part of the electrodes (13a, 13b) is exposed. In this way, after the pad is formed, for example, by dicing the semiconductor substrate 1 in the semiconductor wafer state (silicon wafer state), the thermal humidity sensor (semiconductor chip) in the present modification 1 can be formed. .. For example, a pad formed on a semiconductor chip to be a thermal humidity sensor is electrically connected to a wiring (terminal) of a wiring board (printed circuit board) by using a bonding wire.

<Modification 2>
Subsequently, the modification 2 in the embodiment will be described.

<< Configuration of thermal humidity sensor >>
FIG. 26 is a cross-sectional view showing a schematic configuration of the thermal humidity sensor in the second modification.

In FIG. 26, in the thermal humidity sensor of the second modification, an interlayer film 40 is provided between the heater 11 and the insulating film 30. Other configurations are the same as the configuration of the thermal humidity sensor in the first modification.

For example, the insulating film 30 formed so as to cover the heater 11 is composed of an aluminum nitride film or a silicon nitride film. Here, the silicon nitride film has a property that the adhesion to the refractory metal film (for example, a molybdenum film) constituting the heater 11 is not so good. For example, when the insulating film 30 is made of a silicon nitride film, the refractory metal film constituting the heater 11 and the silicon nitride film constituting the insulating film 30 are in close contact with each other, but the refractory metal film and silicon nitride are in close contact with each other. Since the adhesion to the film is weak, the insulating film 30 may be peeled off from the heater 11 due to heat treatment or the like applied during the manufacturing process.

In this regard, in the present modification 2, for example, an intermediate film 40 made of a silicon oxide film is inserted between the heater 11 and the insulating film 30. In this case, since the adhesion between the refractory metal film constituting the heater 11 and the silicon oxide film constituting the intermediate film 40 is good, peeling of the insulating film 30 from the heater 11 can be suppressed. Further, since the adhesion between the silicon oxide film constituting the interlayer film 40 and the silicon nitride film constituting the insulating film 30 is also good, the adhesion between the intermediate film 40 and the insulating film 30 can be improved. ..

From the above, in the present modification 2, by providing the interlayer film 40 between the heater 11 and the insulating film 30, the adhesion between the heater 11 and the interlayer film 40 is improved, and the interlayer film 40 and the insulating film 30 are provided. It is possible to realize both improvement of the adhesion with and. Thereby, according to the present modification 2, it is possible to provide a highly reliable thermal humidity sensor.

<< Manufacturing method of thermal humidity sensor >>
In the second modification, after the heater 11 is formed, the interlayer film 40 having a film thickness smaller than that of the heater 11 is formed. The interlayer film 40 is composed of, for example, a silicon oxide film formed by using a plasma CVD method. At this time, the film thickness of the silicon oxide film constituting the intermediate film 40 is, for example, about 50 nm. After that, an insulating film 30 made of, for example, a silicon nitride film is formed on the interlayer film 40. The film thickness of this silicon nitride film is about 100 nm.

Subsequent steps are almost the same as the manufacturing method of the thermal humidity sensor in the first modification. As described above, the thermal humidity sensor according to the second modification can be manufactured.

The interlayer film 40 is not limited to the silicon oxide film, and is composed of, for example, a silicon oxide film containing nitrogen, a silicon oxide film containing carbon, an aluminum oxide film, a metal oxide film having non-conductivity, and the like. You can also. In particular, it is desirable that the interlayer film 40 is made of, for example, a film having a melting point of 1000 ° C. or higher and having excellent heat resistance.

<Modification 3>
Next, a modification 3 in the embodiment will be described.

<< Configuration of thermal humidity sensor >>
FIG. 27 is a cross-sectional view showing a schematic configuration of the thermal humidity sensor in the present modification 3.

In FIG. 27, in the thermal humidity sensor of the third modification, an insulating film 45 having a linear expansion coefficient close to the linear expansion coefficient of the refractory metal constituting the heater 11 is formed on the lower layer of the heater 11. That is, an insulating film 45 having tensile stress is formed in the lower layer of the heater 11. The insulating film 45 is made of the same material as the insulating film 30 formed so as to cover the heater 11. For example, the film thickness of the insulating film 45 is thinner than the film thickness of the insulating film 30. Other configurations are the same as the configuration of the thermal humidity sensor in the first modification. As described above, in the thermal humidity sensor in the third modification, the insulating film 45 formed below the insulating film 30, has tensile stress, and has a flat surface is formed in the lower layer of the heater 11. ..

For example, if the insulating film 5 (silicon oxide film) having compressive stress is formed in the lower layer of the heater 11 so as to be in contact with the heater 11, when the heater 11 is heated, the contact portion between the heater 11 and the insulating film 5 is formed. Generates a large thermal stress. Since this thermal stress causes fluctuations in the resistance value of the heater 11, it is desirable to reduce it.

In this regard, in the present modification 3, the insulating film 45 having tensile stress is formed in the lower layer of the heater 11 so as to be in contact with the heater 11. As a result, when the heater 11 is heated, a tensile stress is applied to the heater 11 itself, and a tensile stress is also applied to the insulating film 45 located in the lower layer of the heater 11. Therefore, the thermal stress at the contact portion between the heater 11 and the insulating film 45 can be reduced. As a result, according to the present modification 3, fluctuations in the resistance value of the heater 11 can be suppressed.

Further, it is desirable that the insulating film 45 is made of a material having high thermal conductivity. This is because the insulating film 45 located in the lower layer of the heater 11 is made of a material having high thermal conductivity, so that the temperature distribution in the heater forming region can be made uniform. This means that it becomes easy to suppress the plastic deformation in the central portion of the heater forming region where the temperature tends to be high, and thereby the detection accuracy of the thermal humidity sensor can be maintained for a long period of time.

<< Manufacturing method of thermal humidity sensor >>
In the present modification 3, the insulating film 5 made of the silicon oxide film is formed, and then the insulating film 45 is formed on the insulating film 5. The insulating film 45 is formed of, for example, an aluminum nitride film, and can be formed, for example, by using a sputtering method. The film thickness of the insulating film 45 is, for example, about 50 nm. Next, the insulating film 45 is patterned by using a photolithography technique and an etching technique. The patterning of the insulating film 45 is performed so that the insulating film 45 remains only in the heater forming region. This is because the heat conductivity of the insulating film 45 made of the aluminum nitride film is high, so that when the insulating film 45 is formed so as to extend to the outer region of the heater forming region, the heat generated from the heater formed in the heater forming region is generated. However, it is considered that the heat is easily diffused to the outer region of the heater forming region (heat escape) to suppress the increase in power consumption. Subsequent steps are almost the same as the manufacturing method of the thermal humidity sensor in the first modification. As described above, the thermal humidity sensor according to the third modification can be manufactured.

It is desirable that the film thickness of the insulating film 45 is thinner than the film thickness of the heater 11 and thinner than the film thickness of the insulating film 30 covering the heater 11. This is because when the film thickness of the insulating film 45 becomes thicker, the thermal stress caused by the linear expansion of the insulating film 45 becomes too large.

<Modification example 4>
Subsequently, the modified example 4 in the embodiment will be described.

<< Configuration of thermal humidity sensor >>
FIG. 28 is a cross-sectional view showing a schematic configuration of the thermal humidity sensor in the present modification 4.

In FIG. 28, in the thermal type humidity sensor in the present modification 4, the insulating film 30 has a first film portion 30a formed in a gap between the first portion 11a and the second portion 11b constituting the heater 11. It is composed of a second film portion 30b formed on the first portion 11a and the second portion 11b, and the first film portion 30a and the second film portion 30b are separated from each other. In other words, in the thermal humidity sensor in the present modification 4, the insulating film 30 is not formed on the side wall of the first portion 11a and the side wall of the second portion 11b constituting the heater 11. Other configurations are the same as the configuration of the thermal humidity sensor in the first modification.

In the thermal humidity sensor in the present modification 4 configured in this way, the insulating film 30 is not formed on the side wall of the first portion 11a and the side wall of the second portion 11b constituting the heater 11, so that the first portion 11a is formed. Even if the distance between the second portion 11b and the second portion 11b is reduced, a part of the insulating film 30 having tensile stress (first film portion 30a) and the insulating film 6 having compressive stress can be embedded in this gap. can. Then, in the present modification 4, the volume of the insulating film 6 embedded in the gap between the first portion 11a and the second portion 11b constituting the heater 11 can be reduced. This means that the volume of the insulating film 6 that is easily plastically deformed can be reduced, which means that the gap itself between the first portion 11a and the second portion 11b constituting the heater 11 is less likely to be plastically deformed. As a result, the deflection of the heater 11 can be suppressed. Therefore, in the present modification 4, it is possible to further suppress the change over time in the resistance value of the heater 11 due to the plastic deformation of the insulating film 6 having compressive stress. Further, the fact that the volume (volume) of the gap between the first portion 11a and the second portion 11b constituting the heater 11 can be reduced means that the heat generating portion of the heater 11 (for example, the first portion 11a and the second portion 11b) can be reduced. ) Can be improved, thereby improving the heat generation efficiency of the heater 11. The fact that the heat generation efficiency of the heater 11 can be improved means that the power consumption of the thermal humidity sensor can be reduced. From the above, according to the thermal humidity sensor in the present modification 4, the detection accuracy of the thermal humidity sensor can be maintained for a long period of time while reducing the power consumption.

<< Manufacturing method of thermal humidity sensor >>
In the present modification 4, the insulating film 30 is formed after the heater 11 is formed. Specifically, using a photolithography technique, the photoresist film is patterned so as to open only the heater forming region. Then, using the patterned photoresist film as a mask, for example, an insulating film 30 made of a first film portion 30a made of an aluminum nitride film and a second film portion 30b is formed by a long slow sputtering method having high directivity. That is, when the long slow sputtering method is used, almost no aluminum nitride film is formed on the side wall of the first portion 11a and the side wall of the second portion 11b constituting the heater 11. Subsequent steps are almost the same as the manufacturing method of the thermal humidity sensor in the first modification. As described above, the thermal humidity sensor according to the present modification 4 can be manufactured.

Although the invention made by the present inventor has been specifically described above based on the embodiment thereof, the present invention is not limited to the embodiment and can be variously modified without departing from the gist thereof. Needless to say.

In the embodiment, the thermal type humidity sensor is taken as an example of the thermal type sensor to explain the technical idea in the embodiment, but the technical idea in the embodiment is not limited to this, for example. It can be applied to a wide range of thermal sensors such as thermal flow sensors and thermal gas sensors. This is because, for example, a thermal flow sensor uses a heater to heat a gas and utilizes the fact that the temperature difference between the temperature on the upstream side and the temperature on the downstream side of the warmed gas changes according to the flow rate of the gas. This is because it is a sensor that measures the flow rate of gas and uses a heater. Further, in the thermal gas sensor, for example, a reset operation is performed to release the gas molecules adsorbed by heating by the heater, so that the heater is inevitably used.

The embodiment includes the following embodiments.

(Appendix 1)
Support board and
The insulating film formed on the support substrate and
With the resistance wiring formed on the insulating film,
It is a thermal sensor equipped with
The resistance wiring is
The first part extending in the first direction and
The second part parallel to the first part,
Including
The thermal sensor has a first film formed between the first portion and the second portion, and the thickness in the film thickness direction is smaller than the thickness of the resistance wiring.
The first film is a thermal sensor having a linear expansion coefficient of 1.0 × 10 ^-6 / K or more and 9.0 × 10 ^-6 / K or less.

1 Semiconductor substrate 2 Insulation film 3 Insulation film 4 Insulation film 5 Insulation film 6 Insulation film 7 Insulation film 8 Insulation film 10 Diaphragm 11 Heater 11a 1st part 11b 2nd part 30 Insulation film 30a 1st film part 30b 2nd film part 40 Intermediate film 45 Insulating film

Claims (15)

Support board and
The insulating film formed on the support substrate and
With the resistance wiring formed on the insulating film,
It is a thermal sensor equipped with
The resistance wiring is
The first part extending in the first direction and
The second part parallel to the first part,
Including
The thermal sensor is a first film formed between the first portion and the second portion, has tensile stress, and has a thickness in the film thickness direction smaller than the thickness of the resistance wiring. Has a thermal sensor. In the thermal sensor according to claim 1,
The first film is a thermal sensor in contact with the insulating film. In the thermal sensor according to claim 1,
The occupied volume of the first film formed between the first portion and the second portion is 1/3 or more of the volume between the first portion and the second portion. .. In the thermal sensor according to claim 1,
The first film is a thermal sensor that is also formed on the first portion and the second portion. In the thermal sensor according to claim 1,
The thermal sensor is a thermal sensor having an interlayer film between the resistance wiring and the first film. In the thermal sensor according to claim 1,
The thermal sensor is a thermal sensor further formed above the first film, has tensile stress, and includes a second film having a flat surface. In the thermal sensor according to claim 1,
The thermal sensor is a thermal sensor further formed below the first film, has tensile stress, and includes a third film having a flat surface. In the thermal sensor according to claim 1,
The thermal sensor is
In the plan view, the first region where the resistance wiring is formed and
In a plan view, the second region outside the first region and
Including
The first film is a thermal sensor formed in the first region in a plan view. In the thermal sensor according to claim 1,
The first film is a thermal sensor, which is a stress relaxation film that relieves stress that causes bending of the resistance wiring. In the thermal sensor according to claim 1,
The first film is a thermal sensor, which is an aluminum nitride film or a silicon nitride film. In the thermal sensor according to claim 1,
A thermal sensor in which the width of the resistance wiring in the second direction orthogonal to the first direction is larger than the distance between the first portion and the second portion. In the thermal sensor according to claim 1,
The thermal sensor is a thermal sensor, which is a humidity sensor. (A) Step of forming an insulating film on the support substrate,
(B) Step of forming resistance wiring on the insulating film,
(C) A step of forming a first film covering the resistance wiring,
Is a method of manufacturing a thermal sensor, which is equipped with
The resistance wiring is
The first part extending in the first direction and
The second part parallel to the first part,
Including
A method for manufacturing a thermal sensor, wherein the first film has tensile stress and the thickness in the film thickness direction is smaller than the thickness of the resistance wiring. The first semiconductor chip on which the thermal sensor is formed and
A second semiconductor chip in which a control circuit for controlling the thermal sensor is formed, and
Is a semiconductor device that has
The first semiconductor chip is
Support board and
The insulating film formed on the support substrate and
With the resistance wiring formed on the insulating film,
Equipped with
The resistance wiring is
The first part extending in the first direction and
The second part parallel to the first part,
Including
The first semiconductor chip is formed between the first portion and the second portion, has tensile stress, and has a thickness in the film thickness direction smaller than the thickness of the resistance wiring. A semiconductor device having a film. In the semiconductor device according to claim 14,
The semiconductor device is a semiconductor device that is a sensor module that can be incorporated into an internal combustion engine.

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