WO2019215981A1 - Thermal-type sensor device - Google Patents

Thermal-type sensor device Download PDF

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Publication number
WO2019215981A1
WO2019215981A1 PCT/JP2019/005500 JP2019005500W WO2019215981A1 WO 2019215981 A1 WO2019215981 A1 WO 2019215981A1 JP 2019005500 W JP2019005500 W JP 2019005500W WO 2019215981 A1 WO2019215981 A1 WO 2019215981A1
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Prior art keywords
insulating film
film
sensor device
region
tensile
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PCT/JP2019/005500
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French (fr)
Japanese (ja)
Inventor
中野　洋
佐久間　憲之
松本　昌大
保夫 小野瀬
太田　和宏
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日立オートモティブシステムズ株式会社
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Publication of WO2019215981A1 publication Critical patent/WO2019215981A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
    • G01F1/69—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
    • G01F1/692—Thin-film arrangements

Definitions

  • the present invention relates to a thermal sensor device in which a heating element is formed in a thin film portion covering a cavity formed in a substrate.
  • Patent Document 1 describes an airflow sensor that can increase the mechanical strength by increasing the thickness of the lower thin film and the upper thin film that hold the heating element film of the thin film heating portion, and that reduces the overall warpage.
  • This airflow sensor has a thin film heat generating portion having a structure in which a lower thin film, a heater layer, and an upper thin film are laminated so as to bridge a cavity formed in a silicon substrate.
  • the lower thin film and the upper thin film are each configured by combining a compressive stress film and a tensile stress film, and are laminated so that the lower thin film and the upper thin film have a symmetrical structure with the heater layer interposed therebetween.
  • the compressive stress film is composed of a SiO 2 film having good adhesion
  • the tensile stress film is composed of four Si 3 N 4 films having good moisture resistance.
  • the compressive stress film and the tensile stress film cancel the internal stress, so that the internal stress can be relaxed, and the warp moment can be canceled to suppress the entire warp.
  • the airflow sensor disclosed in Patent Document 1 increases the film thickness of the lower thin film and the upper thin film to improve the mechanical strength (see abstract and paragraph 0009).
  • thermo humidity sensor that detects a change in the amount of heat released from a heating element due to humidity
  • a high temperature and high stress environment causes plastic deformation of the heating element.
  • the thermal stress applied to the heating element it is necessary to minimize the difference in thermal expansion between the heating element and the surrounding thin film.
  • the expansion coefficient of the thin film portion on which the heating element is laminated needs to be as close as possible to the metal material.
  • the thin film portion is warped and becomes an irregular thin film portion, and mechanical strength and productivity are impaired.
  • An object of the present invention is to provide a thermal sensor device capable of reducing stress applied to a heating element and suppressing warpage of a thin film portion under a high temperature environment.
  • the thermal sensor device of the present invention comprises: In a thermal sensor device comprising a thin film portion in which a cavity formed in a substrate is covered with an insulating film, and a heating element formed in the thin film portion, The insulating film in the thin film portion is provided with a compressive region having a partially enhanced compressibility, and the heating element is disposed in the compressive region.
  • Example 1 It is a top view which concerns on one Example (Example 1) of the sensor element used for the thermal sensor apparatus of this invention. It is a circuit diagram which shows one Example of the drive circuit (circuit structure) of the thermal type sensor apparatus of this invention. It is sectional drawing which shows notionally the deformation
  • FIG. 4 is a cross-sectional view showing a cross section of IVA-IVA in FIG.
  • FIG. 3 is a diagram in which a thin film portion 4, a detection heater 5, a tensile region A, and a compressive region B are projected on a virtual plane parallel to the substrate surface (insulating film forming surface) of the substrate 2. It is a figure which shows the temperature dependence of the stress in one Example of the sensor element which concerns on this invention.
  • FIG. 4 is a diagram in which a thin film portion 4, a detection heater 5, a tensile region A, a compressive region B, and a buffer region C are projected on a virtual plane parallel to the substrate surface (insulating film forming surface) of the substrate 2. It is sectional drawing which concerns on one Example (Example 4) of the sensor element used for the thermal sensor apparatus of this invention. It is sectional drawing which concerns on one Example (Example 5) of the sensor element used for the thermal sensor apparatus of this invention.
  • a thermal sensor device in which a heating element is formed in a thin film portion having a thickness of several ⁇ m using a semiconductor process is known.
  • a thermal sensor device that measures the flow rate and concentration of gas utilizes the fact that the amount of heat released from a heating element formed in a thin film portion varies depending on the flow and concentration of gas.
  • a catalyst layer is provided in the thin film portion, and a heating element for activating the catalyst layer so as to react with the combustible gas is provided.
  • Such a sensor device is required to maintain a constant detection sensitivity for a change in a physical quantity of gas for a long period of time.
  • the heating element when the heating element is heated to a high temperature of several hundred degrees for a long time, the heating element and the thin film portion are deformed due to thermal stress. If it does so, the resistance value of a heat generating body will change and a deviation will arise in the heating temperature of a heat generating body. As a result, the detection sensitivity with respect to the change in the physical quantity of the gas changes, and an error occurs in the sensor device.
  • the thermal stress applied to the heating element it is necessary to reduce the difference in thermal expansion between the heating element and the surrounding thin film as much as possible.
  • the expansion coefficient of the thin film portion on which the heating element is laminated needs to be as close as possible to the metal material.
  • the thin film portion is warped and becomes an irregular thin film portion, and mechanical strength and productivity are impaired.
  • a heating element is formed in a thin film part covering a cavity formed in a substrate, and the combined stress of the thin film part in which the heating element is arranged is different from the thin film part in the other region.
  • the thin film portions are formed differently. Thereby, the stress applied to the heating element can be reduced and the warpage of the thin film portion can be suppressed.
  • the thermal sensor device according to the present embodiment provides a thermal sensor device that can maintain measurement accuracy for a long period of time or suppress a decrease in measurement accuracy and ensure mechanical reliability and productivity. can do.
  • Example 1 an embodiment as a thermal sensor device to which the present invention is applied will be described.
  • the present invention is applied to a thermal sensor device that measures intake air humidity of an automobile engine as an example of a thermal sensor device.
  • the physical quantity to be detected by the thermal sensor device of this embodiment is a change in gas concentration
  • the present invention can be applied to a thermal sensor device that measures, for example, hydrogen concentration in addition to humidity.
  • the present invention can also be applied to a flow sensor that detects the flow rate of gas, and the types of gases and physical quantities to be detected are not limited to the following examples.
  • the intake humidity that is measured by the thermal sensor device of this embodiment is measured by detecting a change in the thermal conductivity of the gas due to the gas concentration.
  • the change in thermal conductivity is detected from the change in the amount of heat released from the heating element formed in the sensor element. Since the change in the thermal conductivity of the gas due to the gas concentration is minute, it is necessary to heat the heating element to a high temperature of about 500 ° C. In such a sensor device, the effect of the configuration of the present invention is high.
  • FIG. 1 is a plan view according to one embodiment (Example 1) of a sensor element used in the thermal sensor device of the present invention.
  • the sensor element 1 is formed using a semiconductor microfabrication technique or an etching technique using photolithography.
  • a sensor element (thermal sensor element) 1 has a substrate 2 formed of single crystal silicon.
  • the substrate 2 includes a thin film portion 4 formed with a cavity portion 3 formed by covering the cavity portion 3 with an insulating film.
  • the thin film portion 4 is provided with a detection heater 5 and an auxiliary heater 6 as heating elements.
  • the detection heater 5 and the auxiliary heater 6 are formed as a resistance pattern extending along the plane (film surface) of the thin film portion 4 and having a plurality of folded portions.
  • Detecting heater 5 is used for humidity detection.
  • the detection heater 5 is controlled to a constant temperature of about 500 ° C., for example.
  • the amount of heat released from the detection heater 5 changes depending on the humidity of the atmosphere, and the power required to keep the detection heater 5 at 500 ° C. changes. Humidity can be detected by measuring this power change.
  • the material of the detection heater 5 is preferably a material that is stable at a high temperature and has a high resistance temperature coefficient.
  • metal materials such as platinum (Pt), tantalum (Ta), molybdenum (Mo), and tungsten (W) are suitable.
  • the auxiliary heater 6 is laid so as to surround the detection heater 5.
  • the auxiliary heater 6 can be made of the same material as the detection heater 5.
  • the role of the auxiliary heater 6 is to keep the ambient temperature of the detection heater 5 constant so that the heat radiation amount of the detection heater 5 does not depend on the environmental temperature.
  • the temperature of the auxiliary heater 6 is about 300 ° C., and is set lower than the temperature of the detection heater 5.
  • the auxiliary heater 6 is provided around the detection heater 5 so as to surround the detection heater 5, but the auxiliary heater 6 is not essential in order to obtain the effect of the present invention.
  • the auxiliary heater 6 is for compensating the temperature dependence due to the environmental temperature, and the effect of the present invention can be obtained even in a configuration without the auxiliary heater 6.
  • the substrate 2 is provided with electrode pads 7a to 7d for connecting the detection heater 5 and the auxiliary heater 6 to an external drive circuit.
  • Aluminum (Al) or the like is selected for these electrode pads 7a to 7d.
  • FIG. 2 is a circuit diagram showing an embodiment of a drive circuit (circuit configuration) of the thermal sensor device of the present invention.
  • the thermal sensor device 100 is the entire drive circuit including the sensor element 1.
  • the thermal sensor device 100 described in the first embodiment is also applied to other embodiments.
  • the drive circuit includes a detection heater 5 and an auxiliary heater 6, a bridge circuit (first bridge circuit) BC1 that controls heating of the detection heater 5, and a bridge circuit (second bridge circuit) BC2 that controls heating of the auxiliary heater 6. Become.
  • the bridge circuit BC1 including the detection heater 5 has a configuration in which a series circuit in which the resistor 8a is connected to the detection heater 5 and a series circuit in which the resistor 8b and the resistor 8c are connected are connected in parallel.
  • the potential of the connection portion (intermediate portion) between the detection heater 5 and the resistor 8a (first intermediate potential) and the potential of the connection portion (intermediate portion) between the resistors 8b and 8c (second intermediate potential) are a differential amplifier. It is input to 9a.
  • the differential amplifier 9a outputs a voltage or current corresponding to the difference in input voltage (potential difference between the first intermediate potential and the second intermediate potential).
  • the output of the differential amplifier 9a is connected between the detection heater 5 of the bridge circuit BC1 and the resistor 8b, and is fed back as a heating current of the detection heater 5.
  • the bridge circuit BC2 including the auxiliary heater 6 has a configuration in which a series circuit in which the resistor 10a is connected to the auxiliary heater 6 and a series circuit in which the resistor 10b and the resistor 10c are connected are connected in parallel.
  • the potential (third intermediate potential) at the connection portion (intermediate portion) between the auxiliary heater 6 and the resistor 10a and the potential (fourth intermediate potential) at the connection portion (intermediate portion) between the resistors 10b and 10c are the differential amplifier. 9b.
  • the differential amplifier 9b outputs a voltage or current corresponding to the difference in input voltage (potential difference between the third intermediate potential and the fourth intermediate potential).
  • the output of the differential amplifier 9b is connected between the auxiliary heater 6 of the bridge circuit BC2 and the resistor 10b, and is fed back as a heating current of the auxiliary heater 6.
  • the detection heater 5 is made of a metal material, and the surrounding insulating film is made of silicon oxide or silicon nitride. Since the metal material has a large linear expansion coefficient, when heated to a high temperature, expansion is hindered by the surrounding insulating film, and compressive stress acts on the detection heater 5. If the compressive stress is small, the detection heater 5 is elastically deformed even when stress is applied to it. Therefore, the detection heater 5 returns to its original shape when cooled. However, when the thermal stress increases by heating to a high temperature, the detection heater 5 becomes plastically deformed beyond the elastic deformation region, and residual stress accumulates. As a result, the resistance value of the detection heater 5 gradually changes and affects the measurement accuracy.
  • the insulating film is formed by stacking a silicon oxide film having compressive stress and a silicon nitride film having tensile stress. Since the metal material used for the detection heater 5 is compressive, it is desirable that the insulating film be formed of silicon oxide having the same compressive stress as the detection heater.
  • FIG. 3 shows the warp shape when the thin film portion 4 is tensile and compressive.
  • FIG. 3A is a cross-sectional view conceptually showing deformation of a sensor element used in a thermal sensor device, where the film thickness is set so that the composite stress of the laminated film forming the thin film portion becomes tensile. It is a figure which shows the cross-sectional shape of a thin film part.
  • a thin film portion 4 is formed by laminating a silicon oxide film and a silicon nitride film. Each film thickness is set so that the combined stress of the silicon oxide film and the silicon nitride film becomes tensile. In this case, as shown to FIG. 3A, the thin film part 4 becomes a flat shape and can be manufactured favorably.
  • FIG. 3B is a cross-sectional view conceptually showing deformation of the sensor element used in the thermal sensor device, and when the film thickness is set so that the combined stress of the laminated film forming the thin film portion becomes compressive, It is a figure which shows the cross-sectional shape of a thin film part.
  • each film thickness is set so that the combined stress of the silicon oxide film and the silicon nitride film is tensile.
  • the ratio of the silicon oxide film of the thin film portion 4 is increased to make it compressible, the thin film portion 4 is bent and mechanical strength is lowered as shown in FIG. 3B.
  • FIG. 4A is a cross-sectional view showing the IVA-IVA cross section of FIG.
  • a compressible insulating film 11a is formed on the surface of a substrate 2 made of single crystal silicon.
  • the compressible insulating film 11a is mainly made of silicon oxide (SiO 2), and can be formed by a thermal oxide film or CVD (Chemical Vapor Deposition).
  • a tensile insulating film 12a is formed on the compressible insulating film 11a.
  • the tensile insulating film 12a for example, a silicon nitride film (Si3N4) formed by a CVD method can be used.
  • a portion (detection heater forming region corresponding portion) 12a-1 corresponding to the region B where the detection heater 5 is formed is partially removed by etching. That is, the tensile insulating film 12a is formed when the tensile insulating film 12a and the detection heater 5 are projected on the plane (insulating film forming surface) 2a of the substrate 2 or a virtual plane parallel to the plane 2a. The portion 12a-1 that overlaps the region to be removed is removed.
  • a compressible insulating film 11b made of silicon oxide is formed by the same method.
  • the surface of the compressible insulating film 11b is planarized as necessary by CMP (Chemical-mechanical polishing) or the like.
  • the detection heater 5 and the auxiliary heater 6 are formed by forming and patterning a metal film by sputtering or the like.
  • Mo molybdenum
  • platinum, tantalum, tungsten and the like can also be used.
  • a compressive insulating film 11c made of silicon oxide is formed using a plasma CVD method or the like.
  • the portion of the substrate 2 where the detection heater 5 and the auxiliary heater 6 are located is anisotropically etched using potassium hydroxide (KOH) or the like to form the cavity 3.
  • KOH potassium hydroxide
  • the combined stress of the insulating film in the region B where the detection heater 5 is formed needs to be compressible. Therefore, in this embodiment, by partially removing the tensile insulating film 12a, the ratio of the compressive insulating films 11a, 11b, and 11c in the region B where the detection heater 5 is formed is changed to the region of the other thin film portion 4. Increased compared to A. That is, a compressive region B in which the combined stress of the thin film portion 4 formed of the insulating films 11a, 12a, 11b, and 11c is partially compressive is provided, and the detection heater 5 is disposed in the compressive region B. Yes.
  • the region B where the detection heater 5 is formed becomes stronger in compressibility ( ⁇ ), and the other region A of the thin film portion 4 becomes tensile (+ ⁇ ). .
  • the distortion caused by the expansion of the region B where the detection heater 5 is formed can be offset in the surface direction by the region A where the surrounding tensile property is strengthened, and the thin film portion 4 is manufactured in a flat shape. be able to.
  • the tensile insulating film 12a in the region where the detection heater 5 is formed is removed, but the region where the auxiliary heater 6 is formed has a structure in which the tensile insulating film 12a remains.
  • the detection heater 5 has a high temperature and a large thermal stress, but the auxiliary heater 6 has a lower temperature than the detection heater 5 and is less affected by the thermal stress.
  • the removal range can be adjusted as appropriate, for example, by removing the tensile insulating film 11b even in the region where the auxiliary heater 6 is formed.
  • the tensile insulating film 12a in the region B where the detection heater 5 is disposed is completely removed.
  • the tensile insulating film is partially formed below the detection heater 5. It is good also as a structure which left 12a.
  • partially leaving the tensile insulating film 12a means that when two or more tensile insulating films 12a are provided, the detection heater forming region corresponding portion 12a-1 is removed from all the tensile insulating films 12a. It is not necessary, and if the region B is compressible, it means that there may be a layer of the tensile insulating film 12a from which the detection heater forming region corresponding portion 12a-1 is not removed.
  • partially leaving the tensile insulating film 12a means that at least one tensile insulating film 12a composed of one layer or a plurality of layers is configured to be thin.
  • the degree to which the tensile insulating film 12a below the detection heater 5 is removed can be designed according to the required specifications of the system to which the thermal sensor device 100 is applied.
  • the tensile insulating film 12a is formed on the entire surface outside the region B of the detection heater 5, but there is a portion where the tensile insulating film 12a is partially removed outside the region B. Also good. That is, the effect of the present invention can be obtained as long as the tensile strength is high enough to absorb the stress accompanying the compression of the upper and lower insulating films of the detection heater 5.
  • the tensile insulating film 12a to be partially removed is formed so as to be sandwiched between the compressive insulating films 11a, 11b, and 11c.
  • the reason for this is that, by adopting a configuration in which a partially removed film is interposed in a layer close to the intermediate layer in the thin film portion 4, the change in the warping moment due to the planar position of the thin film portion 4 is reduced, and the flatness without unevenness is reduced. This is because the thin film portion 4 can be formed.
  • the tensile insulating film 12a is formed on the lower layer side of the heating elements such as the detection heater 5 and the auxiliary heater 6, but the tensile insulating film 12a is formed on the upper layer side of these heating elements.
  • a structure in which the tensile insulating film 12a in the region where the heating element is formed is partially removed may be employed. In this case, a silicon nitride film using a plasma CVD method or the like can be used.
  • a silicon nitride film is used as the material of the tensile insulating film 12a forming the thin film portion 4.
  • the material is not limited to the silicon nitride film, and the same configuration is possible as long as the material has tensile stress. Can be.
  • aluminum nitride or the like can be used as a material for the tensile insulating film 12a.
  • the internal stress of the thin film portion 4 formed by the laminated film of the silicon nitride film and the silicon oxide film varies depending on the temperature.
  • FIG. 4B is a diagram in which the thin film portion 4, the detection heater 5, the tensile region A, and the compressive region B are projected on a virtual plane parallel to the substrate surface (insulating film forming surface) of the substrate 2.
  • the tensile insulating film 12a in the region B where the detection heater 5 is located is removed in a square shape.
  • the shape to be removed is a polygon or a circle, thereby reducing the stress concentration at the corner and suppressing the strength reduction of the thin film portion 4. it can.
  • FIG. 5 is a diagram showing the temperature dependence of stress in one embodiment of the sensor element according to the present invention.
  • FIG. 5 shows the relationship between the temperature of the thin film portion 4 formed on the single crystal silicon substrate 2 and the internal stress.
  • the thin film portion 4 formed on the substrate 2 made of single crystal silicon has a characteristic that the tensile stress (+ ⁇ ) increases as the temperature increases, and the compressive stress ( ⁇ ) increases as the temperature decreases. .
  • the thin film portion 4 is flat if it is in a high temperature range where tensile stress is applied. However, when the temperature is lowered, the compressibility becomes strong and the thin film portion 4 is warped.
  • the broken line A shown in FIG. 5 is the temperature characteristic of the internal stress of the thin film structure with enhanced tensile properties on the low temperature side (room temperature), and corresponds to the thin film structure in the region A in this embodiment shown in FIG. In the case of the thin film structure in the region A, the tensile property is maintained on the low temperature side and the high temperature side.
  • the solid line B is the temperature characteristic of the internal stress of the thin film structure with enhanced compressibility, and corresponds to the thin film structure of the region B in this embodiment shown in FIG. In the case of the thin film structure in the region B, it becomes tensile on the high temperature side and compressible on the low temperature side (room temperature).
  • the thin film portion 4 of this embodiment has a configuration in which the insulating films having the characteristics of the broken line A and the solid line B are combined.
  • FIG. 6 is a cross-sectional view according to one embodiment (Example 2) of a sensor element used in the thermal sensor device of the present invention.
  • the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
  • the sensor element 20 of the present embodiment will be described below.
  • Compressive insulating film 21a is formed on the surface of substrate 2 made of single crystal silicon.
  • the compressible insulating film 21a is mainly made of silicon oxide (SiO2), and can be formed by a thermal oxide film or CVD (Chemical Vapor Deposition).
  • a tensile insulating film 22a is formed on the compressible insulating film 21a.
  • the tensile insulating film 22a for example, a silicon nitride film (Si3N4) formed by a CVD method can be used.
  • the tensile insulating film 22a is formed with a uniform film thickness so as to completely cover the cavity 3.
  • a compressible insulating film 21b made of silicon oxide is formed on the tensile insulating film 22a in the same manner.
  • a tensile insulating film 22b made of silicon nitride is formed on the compressible insulating film 21b.
  • the portion corresponding to the region B where the detection heater 5 is formed (detection heater formation region corresponding portion) 12a-1 is partially removed by etching.
  • a compressible insulating film 21c made of silicon oxide is formed by the same method.
  • the surface of the compressible insulating film 21c is planarized as necessary by CMP (Chemical mechanical polishing) or the like.
  • the detection heater 5 and the auxiliary heater 6 are formed by forming and patterning a metal film by sputtering or the like.
  • Mo molybdenum
  • a compressive insulating film 21d made of silicon oxide is formed using a plasma CVD method or the like.
  • a tensile insulating film 22c is formed on the compressible insulating film 21d.
  • silicon nitride formed by a plasma CVD method can be used as the tensile insulating film 22c.
  • the compressible insulating film 21e is formed by the same method.
  • the cavity 3 is formed in the substrate 2 on which the detection heater 5 and the auxiliary heater 6 are located by anisotropic etching using potassium hydroxide (KOH) or the like.
  • the compressible insulating film 21b, the tensile insulating film 22b, the compressible insulating film 21c, and the compressible insulating film 21d of the present embodiment are the same as the compressive insulating film 11a, the tensile insulating film 12a, and the compressible insulating film 11b of the first embodiment. And the compressive insulating film 11c. Further, in this embodiment, since the tensile insulating film 22a and the tensile insulating film 22c are added, the lowermost compressive insulating film 21a and the uppermost compressive insulating film 21e are added.
  • the tensile insulating film 12b is partially removed, so that the region B where the detection heater 5 is formed has a configuration in which the compressibility is enhanced as compared with the other regions A. That is, also in this embodiment, the ratio of the compressible insulating film (silicon oxide film) in the region B where the detection heater 5 is formed is increased as compared with the other part A.
  • the region B where the detection heater 5 is formed has a higher compressibility ( ⁇ ), and the other region A of the thin film portion 4 has a higher tensile property (+ ⁇ ). It has been.
  • a compressible region (compressible thin film portion) B and a tensile region (tensile thin film portion) A are formed in the thin film portion 4 provided in the cavity portion 3, and the compressive region (compressible thin film portion).
  • a detection heater 5 is arranged at B.
  • the tensile insulating film 22a and the tensile insulating film 22c that completely cover the region on the cavity 3 are provided. Further, the detection heater 5 is configured to be interposed between the upper tensile insulating film 22c and the lower tensile insulating film 22a. Since the tensile insulating films 22a and 22c are formed of silicon nitride, the tensile insulating films 22a and 22c have an effect of blocking moisture and oxygen entering from the outside, thereby enhancing the effect of protecting the detection heater 5 from oxidation and corrosion.
  • the structures relating to the tensile insulating films 22a and 22c and the compressible insulating film 21a and the compressible insulating film 21e added to provide the tensile insulating films 22a and 22c are different from the first embodiment.
  • Other configurations can be configured in the same manner as in the first embodiment.
  • the silicon nitride film is formed by partially removing the tensile insulating film 22b located in the intermediate layer. In this case, since the film close to the center in the stacking direction of the thin film portion 4 is partially removed, the change in the warping moment at the planar position of the thin film portion 4 is reduced, and a flat thin film without unevenness is formed. be able to.
  • FIG. 7A is a cross-sectional view according to one embodiment (third embodiment) of a sensor element used in the thermal sensor device of the present invention.
  • a configuration is further added to the second embodiment, and the configuration and effects different from the second embodiment will be described.
  • Components similar to those in the first and second embodiments are denoted by the same reference numerals as those in the first and second embodiments, and the description thereof is omitted.
  • the auxiliary heater 6 is not an essential configuration, the description is omitted in FIG. 7, but the auxiliary heater 6 may be provided as in the first and second embodiments.
  • the sensor element 30 of the present embodiment will be described below.
  • the tensile insulating film 22b is partially removed in the region of the detection heater 5.
  • a buffer region C is provided between the region B where the tensile insulating film 22b of the thin film portion 4 is removed and the region A where the tensile insulating film 22b is formed.
  • the buffer region C relaxes a rapid film quality change at the boundary between the region A and the region B, and has a structure in which the tensile insulating film 22b is gradually removed as the detection heater 5 is approached.
  • the buffer region C can be formed by providing slits or holes in the tensile insulating film 12b. For example, a rapid change in film quality is alleviated by changing the width of the slit, the diameter or width of the hole, or changing the interval between the slit and the hole.
  • an external force may act on the thin film portion 4 of the sensor element 30 due to pressure fluctuation or particle impact.
  • stress is generated in the insulating film.
  • the location where the film quality changes on the thin film portion 4 is likely to break due to stress concentration due to bending.
  • the stress concentration can be relaxed and the strength reduction of the thin film portion 4 can be suppressed.
  • FIG. 7B is a diagram in which the thin film portion 4, the detection heater 5, the tensile region A, the compressive region B, and the buffer region C are projected on a virtual plane parallel to the substrate surface (insulating film forming surface) of the substrate 2.
  • the shape of the slit or hole constituting the buffer region C a shape as shown in FIG. 7B can be considered.
  • the shape of the slit or hole may be other than the shape shown in FIG. 7B.
  • the stress concentration at the boundary between the region A and the region B can be reduced by providing the buffer region C from which the tensile insulating film is removed by a slit or a hole at the boundary between the region A and the region B.
  • the shape of the buffer region C shown in FIG. 7B can be applied to the embodiments described later within a consistent range.
  • the effect of relaxing the stress concentration is improved.
  • FIG. 8 is a cross-sectional view according to an embodiment (embodiment 4) of a sensor element used in the thermal sensor device of the present invention.
  • the present embodiment is a modification of the second embodiment, and the configuration and effect different from the second embodiment will be described.
  • the same configurations as those in the first to third embodiments are denoted by the same reference numerals as those in the first to third embodiments, and the description thereof is omitted.
  • the auxiliary heater 6 is not an essential configuration, the description thereof is omitted in FIG. 8, but the auxiliary heater 6 may be provided as in the first and second embodiments.
  • the sensor element 40 of the present embodiment will be described below.
  • This embodiment is effective when the detection heater 5 has a relatively large pattern.
  • a part of the tensile insulating film 22b is left in the region B where the detection heater 5 of the thin film portion 4 is formed. That is, in this embodiment, the structure of the tensile insulating film 22b is partially different from that of the second embodiment. If the formation area of the detection heater 5 is widened, the area to be compressible is also widened. As a result, the area A around the detection heater 5 becomes narrow, and the compressive strain in the area B of the detection heater 5 cannot be sufficiently absorbed.
  • the tensile insulating film 12b is provided in the region B of the detection heater 5 except for the portion immediately below where the detection heater 5 is patterned.
  • the tensile insulating film 12b just under the patterning of the detection heater 5 is removed. That is, the detection heater 5 and the tensile insulating film 12b do not overlap when the thin film portion 4 is viewed from above. That is, when the detection heater 5 and the tensile insulating film 12b are projected on a plan view similar to FIG. 1, the tensile insulating film 12b made of silicon nitride is provided between the metal patterns constituting the detection heater 5. It has been.
  • FIG. 9 is a cross-sectional view according to one embodiment (Example 5) of the sensor element used in the thermal sensor device of the present invention.
  • the compressibility of the region B in which the detection heater 5 is formed is enhanced as compared with other regions A by forming the oxide film serving as a compressible insulating film into a pressure film.
  • the same configurations as those of the first to fourth embodiments are denoted by the same reference numerals as those of the first to fourth embodiments, and the description thereof is omitted.
  • the auxiliary heater 6 is not an essential configuration, the description is omitted in FIG. 9, but the auxiliary heater 6 may be provided in the same manner as in the first and second embodiments.
  • the sensor element 50 of the present embodiment will be described below.
  • a compressible insulating film 51a is formed on the surface of the substrate 2 made of single crystal silicon.
  • the compressible insulating film 51a is mainly made of silicon oxide and can be formed by a thermal oxide film or CVD (Chemical Vapor Deposition).
  • a tensile insulating film 52a is formed on the compressible insulating film 51a.
  • the tensile insulating film 52a for example, a silicon nitride film formed by a CVD method can be used.
  • the tensile insulating film 52a is formed with a uniform film thickness so as to completely cover the cavity 3.
  • a compressive insulating film 51b made of silicon oxide is formed on the tensile insulating film 52a in the same manner.
  • a detection heater 5 and an auxiliary heater 6 are formed by forming a metal film by sputtering or the like and patterning it.
  • a compressive insulating film 51c made of silicon oxide is formed using a plasma CVD method or the like. The compressible insulating film 51c is removed leaving the region where the detection heater 5 is formed.
  • a tensile insulating film 52b is formed.
  • silicon nitride formed by a plasma CVD method can be used.
  • a compressive insulating film 51d made of silicon oxide is formed by the same method.
  • the compressive insulating film (silicon oxide) in the region B where the detection heater 5 is formed is thicker than other regions. That is, a compressive region B in which the combined stress of the thin film portion 4 formed of an insulating film is partially compressible compared to other regions A is provided, and the detection heater 5 is disposed in the compressive region B. Yes. As a result, the region B where the detection heater 5 is formed can be made more compressible than the other regions A, and the other regions A can be made more tensile.
  • the thickness of the entire insulating film forming the thin film portion 4 is different between the region A where the compressive insulating film is formed thick and the region B where the compressive insulating film is formed thin. Therefore, a protrusion (thick film portion) 53 is formed on the surface of the thin film portion 4.
  • the step 53a of the protrusion (thick film portion) 53 is likely to cause stress concentration due to external force as described above. Therefore, it is desirable to reduce the stress concentration by forming the stepped portion 53a so as to have a step whose height changes gently. Specifically, the stepped portion can be relaxed and the film thickness can be changed gently by known methods such as SOG (Spinson Glass), etch back, and CMP.
  • the configuration in which the compressive insulating film 51c in the other region A is removed while leaving the compressible insulating film 51c in the upper layer (region B) of the detection heater 5 has been described.
  • a similar structure can be formed using the insulating film 51b. That is, if the compressive insulating film 51b is formed thicker than the other regions A in the region B where the detection heater 5 is formed, the effect of the present invention can be obtained.
  • the compressive insulating film 51c or the compressive insulating film 51b is not completely removed in the region A, but the film thickness of the compressible insulating film 51c or the compressive insulating film 51b in the region B.
  • the compressive insulating film 51c or the compressive insulating film 51b in the region A is thinned, the effect of the present invention may be obtained.
  • the following thermal sensor device is obtained.
  • the hollow portion 3 formed in the substrate 2 is formed in the thin film portion 4 covered with the insulating films 11a to 11d, 12a to 12c, 21a to 21e, 22a to 22c, 51a to 51d, 52a and 52b, and the thin film portion 4.
  • the thermal sensor device including the heating element 5 the insulating film in the thin film portion 4 is provided with a compressible region B having a partially enhanced compressibility, and the heating element 5 is disposed in the compressive region B.
  • a tensile region A is formed in the insulating film around the compressive region B.
  • the portions of the insulating film covering the cavity 3 are compressed stress films 11a to 11d, 21a to 21e, and 51a to 51d that are compressible with respect to the substrate 2 at room temperature, and the substrate. 2, tensile stress films 12a to 12c, 22a to 22c, 52a, and 52b that are tensile with respect to 2 are partially removed in the compressive region B.
  • the insulating film includes the lower layer side tensile stress film 22a formed on the lower layer side of the heating element 5 and the upper layer side tensile stress film 22c formed on the upper layer side of the heating element 5.
  • the intermediate tensile stress film 22b is formed thicker than the upper tensile stress film 22c and the lower tensile stress film 22a.
  • the portion of the insulating film includes a region C in which the tensile stress film 22b is removed in a slit shape.
  • the tensile stress film 12a is removed in the compressive region B into a polygon or a circle.
  • the compressive stress films 11a to 11d, 21a to 21e, 51a to 51d are insulating films mainly composed of silicon oxide, and the tensile stress films are silicon nitrides 12a to 12c, 22a to 22c, 52a, 52b. It is an insulating film mainly composed of (9)
  • the heating element 5 is a metal material.
  • this invention is not limited to each above-mentioned Example, Various modifications are included.
  • the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations.
  • a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment.

Abstract

The purpose of the present invention is to provide a thermal-type sensor device whereby stress applied to a heating element can be reduced and warping of a thin film part can be suppressed in a high-temperature environment. A thermal-type sensor device provided with a thin film part 4 in which a cavity part 3 formed in a substrate 2 is covered by an insulating film, and a heating element 5 formed on the thin film part 4, wherein a compressible region B in which compressibility is partially increased in insulating films 11a, 12a, 11b, 11c in the thin film part 4 is provided, and the heating element 5 is disposed in the compressible region B.

Description

熱式センサ装置Thermal sensor device
　本発明は、基板に形成した空洞部を覆う薄膜部に発熱体を形成した熱式センサ装置に関する。 The present invention relates to a thermal sensor device in which a heating element is formed in a thin film portion covering a cavity formed in a substrate.
　本技術分野の背景技術として、特開平１１－２７１１２３号公報（特許文献１）がある。特許文献１には、薄膜発熱部の発熱体膜を保持する下部薄膜と上部薄膜の膜厚を厚くして機械的強度を高めることができ、且つ全体の反りを低減したエアフローセンサが記載されている。このエアフローセンサは、シリコン基板に形成した空洞部を架橋するように、下部薄膜、ヒータ層および上部薄膜を積層した構造の薄膜発熱部を有する。下部薄膜及び上部薄膜は、それぞれ圧縮応力膜と引張応力膜とを組み合わせた構成とし、ヒータ層を挟んで下部薄膜と上部薄膜とが対称構造となるように積層される。圧縮応力膜は密着性の良いＳｉＯ２膜で構成し、引張応力膜は、耐湿性の良いＳｉ３Ｎ４膜で４構成している。圧縮応力膜および引張応力膜は、内部応力を打ち消し合うので内部応力を緩和でき、反りモーメントを打ち消して全体の反りを抑制できる。これにより、特許文献１のエアフローセンサは、下部薄膜及び上部薄膜の膜厚を厚くして、機械的強度の向上を図っている（要約および段落０００９参照）。 As background art in this technical field, there is JP-A-11-271123 (Patent Document 1). Patent Document 1 describes an airflow sensor that can increase the mechanical strength by increasing the thickness of the lower thin film and the upper thin film that hold the heating element film of the thin film heating portion, and that reduces the overall warpage. Yes. This airflow sensor has a thin film heat generating portion having a structure in which a lower thin film, a heater layer, and an upper thin film are laminated so as to bridge a cavity formed in a silicon substrate. The lower thin film and the upper thin film are each configured by combining a compressive stress film and a tensile stress film, and are laminated so that the lower thin film and the upper thin film have a symmetrical structure with the heater layer interposed therebetween. The compressive stress film is composed of a SiO 2 film having good adhesion, and the tensile stress film is composed of four Si 3 N 4 films having good moisture resistance. The compressive stress film and the tensile stress film cancel the internal stress, so that the internal stress can be relaxed, and the warp moment can be canceled to suppress the entire warp. As a result, the airflow sensor disclosed in Patent Document 1 increases the film thickness of the lower thin film and the upper thin film to improve the mechanical strength (see abstract and paragraph 0009).
特開平１１－２７１１２３号公報JP-A-11-271123
　気体の物理量の微小な変化を検出するためには、発熱体を高温化し検出感度を上げる必要がある。例えば、湿度による発熱体の放熱量変化を検出する熱式湿度センサにおいては、発熱体を５００℃程度の高温に加熱する必要がある。そうすると、発熱体（発熱体膜）とその周辺の薄膜部との熱膨張差が増加し、発熱体に加わるストレスが増加する。このような高温、高ストレス環境よって、発熱体に塑性変形が生じる。 In order to detect minute changes in the physical quantity of gas, it is necessary to increase the detection sensitivity by raising the temperature of the heating element. For example, in a thermal humidity sensor that detects a change in the amount of heat released from a heating element due to humidity, it is necessary to heat the heating element to a high temperature of about 500 ° C. If it does so, the thermal expansion difference of a heat generating body (heat generating body film | membrane) and the surrounding thin film part will increase, and the stress added to a heat generating body will increase. Such a high temperature and high stress environment causes plastic deformation of the heating element.
　特許文献１のエアフローセンサは、薄膜部の反りを低減することが可能であるが、発熱体に加わる熱ストレスの抑制に対する配慮が十分ではなかった。 Although the air flow sensor of Patent Document 1 can reduce the warpage of the thin film portion, consideration for suppressing thermal stress applied to the heating element is not sufficient.
　発熱体に加わる熱ストレスを低減するためには、発熱体とその周辺の薄膜との熱膨張差をできるだけ小さくすることが必要である。例えば、発熱体に金属材料を用いた場合、発熱体を積層する薄膜部の膨張係数をできるだけ金属材料に近づける必要がる。しかしながら、薄膜部の内部応力を金属材料に合わせようとすると、薄膜部に反りが生じ異形な薄膜部となり、機械的強度や生産性が損なわれる。 In order to reduce the thermal stress applied to the heating element, it is necessary to minimize the difference in thermal expansion between the heating element and the surrounding thin film. For example, when a metal material is used for the heating element, the expansion coefficient of the thin film portion on which the heating element is laminated needs to be as close as possible to the metal material. However, when trying to match the internal stress of the thin film portion to the metal material, the thin film portion is warped and becomes an irregular thin film portion, and mechanical strength and productivity are impaired.
　本発明の目的は、高温環境下において、発熱体に加わるストレスを低減し、薄膜部の反りを抑制することができる熱式センサ装置を提供することにある。 An object of the present invention is to provide a thermal sensor device capable of reducing stress applied to a heating element and suppressing warpage of a thin film portion under a high temperature environment.
　上記目的を達成するために、本発明の熱式センサ装置は、
　基板に形成した空洞部を絶縁膜で覆った薄膜部と、前記薄膜部に形成した発熱体と、を備えた熱式センサ装置において、
　前記薄膜部における前記絶縁膜に部分的に圧縮性を強めた圧縮性領域が設けられ、前記圧縮性領域に前記発熱体を配置する。 In order to achieve the above object, the thermal sensor device of the present invention comprises:
In a thermal sensor device comprising a thin film portion in which a cavity formed in a substrate is covered with an insulating film, and a heating element formed in the thin film portion,
The insulating film in the thin film portion is provided with a compressive region having a partially enhanced compressibility, and the heating element is disposed in the compressive region.
　本発明によれば、発熱体に加わるストレスを低減し、薄膜部の反りを抑制することができる熱式センサ装置を提供することができる。上記した以外の課題、構成及び効果は、以下の実施形態の説明により明からにされる。 According to the present invention, it is possible to provide a thermal sensor device that can reduce the stress applied to the heating element and suppress the warpage of the thin film portion. Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.
本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例１）に係る平面図である。It is a top view which concerns on one Example (Example 1) of the sensor element used for the thermal sensor apparatus of this invention. 本発明の熱式センサ装置の駆動回路（回路構成）の一実施例を示す回路図である。It is a circuit diagram which shows one Example of the drive circuit (circuit structure) of the thermal type sensor apparatus of this invention. 熱式センサ装置に用いられるセンサ素子の変形を概念的に示す断面図であり、薄膜部を形成する積層膜の合成応力が引張性となるように膜厚を設定した場合の、薄膜部の断面形状を示す図である。It is sectional drawing which shows notionally the deformation | transformation of the sensor element used for a thermal sensor apparatus, and is a cross section of a thin film part when setting a film thickness so that the synthetic stress of the laminated film which forms a thin film part may become tensile property It is a figure which shows a shape. 熱式センサ装置に用いられるセンサ素子の変形を概念的に示す断面図であり、薄膜部を形成する積層膜の合成応力が圧縮性となるように膜厚を設定した場合の、薄膜部の断面形状を示す図である。It is sectional drawing which shows notionally the deformation | transformation of the sensor element used for a thermal-type sensor apparatus, and the cross section of a thin film part at the time of setting a film thickness so that the synthetic stress of the laminated film which forms a thin film part may become compressibility It is a figure which shows a shape. 図１のIVA－IVA断面を示す断面図である。FIG. 4 is a cross-sectional view showing a cross section of IVA-IVA in FIG. 薄膜部４、検出ヒータ５、引張性領域Ａ及び圧縮性領域Ｂを基板２の基板面（絶縁膜形成面）に平行な仮想平面に投影した図である。FIG. 3 is a diagram in which a thin film portion 4, a detection heater 5, a tensile region A, and a compressive region B are projected on a virtual plane parallel to the substrate surface (insulating film forming surface) of the substrate 2. 本発明に係るセンサ素子の一実施例における応力の温度依存性を示す図である。It is a figure which shows the temperature dependence of the stress in one Example of the sensor element which concerns on this invention. 本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例２）に係る断面図である。It is sectional drawing which concerns on one Example (Example 2) of the sensor element used for the thermal sensor apparatus of this invention. 本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例３）に係る断面図である。It is sectional drawing which concerns on one Example (Example 3) of the sensor element used for the thermal sensor apparatus of this invention. 薄膜部４、検出ヒータ５、引張性領域Ａ、圧縮性領域Ｂ及び緩衝領域Ｃを基板２の基板面（絶縁膜形成面）に平行な仮想平面に投影した図である。FIG. 4 is a diagram in which a thin film portion 4, a detection heater 5, a tensile region A, a compressive region B, and a buffer region C are projected on a virtual plane parallel to the substrate surface (insulating film forming surface) of the substrate 2. 本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例４）に係る断面図である。It is sectional drawing which concerns on one Example (Example 4) of the sensor element used for the thermal sensor apparatus of this invention. 本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例５）に係る断面図である。It is sectional drawing which concerns on one Example (Example 5) of the sensor element used for the thermal sensor apparatus of this invention.
　気体の物理量を検出して電気信号に変換するセンサ装置として、半導体プロセスを用いて厚さ数μmの薄膜部に発熱体を形成した熱式センサ装置が知られている。例えば、気体の流量、濃度などを測定する熱式センサ装置は、薄膜部に形成した発熱体の放熱量が気体の流れや濃度により変化することを利用している。また、可燃性気体の濃度センサでは、薄膜部に触媒層を設け、この触媒層を可燃性ガスと反応するように活性化させるための発熱体が設けられている。このような、センサ装置は、気体の物理量変化に対する検出感度を長期間一定に保つことが必要である。 As a sensor device that detects a physical quantity of a gas and converts it into an electrical signal, a thermal sensor device in which a heating element is formed in a thin film portion having a thickness of several μm using a semiconductor process is known. For example, a thermal sensor device that measures the flow rate and concentration of gas utilizes the fact that the amount of heat released from a heating element formed in a thin film portion varies depending on the flow and concentration of gas. Further, in the combustible gas concentration sensor, a catalyst layer is provided in the thin film portion, and a heating element for activating the catalyst layer so as to react with the combustible gas is provided. Such a sensor device is required to maintain a constant detection sensitivity for a change in a physical quantity of gas for a long period of time.
　しかしながら、発熱体が数百度の高温に長時間加熱されると、熱ストレスにより発熱体や薄膜部に変形が生じる。そうすると発熱体の抵抗値が変化して発熱体の加熱温度にずれが生じる。その結果、気体の物理量変化に対する検出感度が変化し、センサ装置に誤差が生じる。 However, when the heating element is heated to a high temperature of several hundred degrees for a long time, the heating element and the thin film portion are deformed due to thermal stress. If it does so, the resistance value of a heat generating body will change and a deviation will arise in the heating temperature of a heat generating body. As a result, the detection sensitivity with respect to the change in the physical quantity of the gas changes, and an error occurs in the sensor device.
　また、発熱体に加わる熱ストレスを低減するためには、発熱体とその周辺の薄膜との熱膨張差をできるだけ小さくすることが必要である。例えば、発熱体に金属材料を用いた場合、発熱体を積層する薄膜部の膨張係数をできるだけ金属材料に近づける必要がる。しかしながら、薄膜部の内部応力を金属材料に合わせようとすると、薄膜部に反りが生じ異形な薄膜部となり、機械的強度や生産性が損なわれる。 In order to reduce the thermal stress applied to the heating element, it is necessary to reduce the difference in thermal expansion between the heating element and the surrounding thin film as much as possible. For example, when a metal material is used for the heating element, the expansion coefficient of the thin film portion on which the heating element is laminated needs to be as close as possible to the metal material. However, when trying to match the internal stress of the thin film portion to the metal material, the thin film portion is warped and becomes an irregular thin film portion, and mechanical strength and productivity are impaired.
　本発明に係る熱式センサ装置の一実施例は、基板に形成した空洞部を覆う薄膜部に発熱体を形成し、発熱体が配置された薄膜部の合成応力が他の領域の薄膜部と異なるように薄膜部を形成する。これにより、発熱体に加わるストレスを低減するとともに薄膜部のそりを抑制することができる。その結果、本実施例の熱式センサ装置は、長期間に亘り測定精度の維持または測定精度の低下抑制を図ることができるとともに、機械的信頼性および生産性を確保した熱式センサ装置を提供することができる。 In one embodiment of the thermal sensor device according to the present invention, a heating element is formed in a thin film part covering a cavity formed in a substrate, and the combined stress of the thin film part in which the heating element is arranged is different from the thin film part in the other region. The thin film portions are formed differently. Thereby, the stress applied to the heating element can be reduced and the warpage of the thin film portion can be suppressed. As a result, the thermal sensor device according to the present embodiment provides a thermal sensor device that can maintain measurement accuracy for a long period of time or suppress a decrease in measurement accuracy and ensure mechanical reliability and productivity. can do.
　［実施例１］
　以下、本発明を適用してなる熱式センサ装置としての実施形態を説明する。以下で説明する実施例は、熱式センサ装置の一例として、自動車エンジンの吸気湿度を計測する熱式センサ装置に本発明を適用したものである。本実施例の熱式センサ装置が検出対象とする物理量は気体の濃度変化であり、本発明は湿度の他に例えば水素濃度などを計測する熱式センサ装置にも適用できる。また本発明は気体の流量を検出するフローセンサにも適用可能であり、検出対象とする気体や物理量の種類は以下の実施例に限定されない。 [Example 1]
Hereinafter, an embodiment as a thermal sensor device to which the present invention is applied will be described. In the embodiment described below, the present invention is applied to a thermal sensor device that measures intake air humidity of an automobile engine as an example of a thermal sensor device. The physical quantity to be detected by the thermal sensor device of this embodiment is a change in gas concentration, and the present invention can be applied to a thermal sensor device that measures, for example, hydrogen concentration in addition to humidity. The present invention can also be applied to a flow sensor that detects the flow rate of gas, and the types of gases and physical quantities to be detected are not limited to the following examples.
　本実施例の熱式センサ装置が計測対象とする吸気湿度は、気体の濃度による気体の熱伝導率変化を検出することにより計測される。熱伝導率の変化はセンサ素子に形成した発熱体の放熱量変化から検出する。気体の濃度による気体の熱伝導率変化は微小であることから、発熱体を５００℃程度の高温に加熱する必要がある。このようなセンサ装置においては本発明の構成による効果が高い。 The intake humidity that is measured by the thermal sensor device of this embodiment is measured by detecting a change in the thermal conductivity of the gas due to the gas concentration. The change in thermal conductivity is detected from the change in the amount of heat released from the heating element formed in the sensor element. Since the change in the thermal conductivity of the gas due to the gas concentration is minute, it is necessary to heat the heating element to a high temperature of about 500 ° C. In such a sensor device, the effect of the configuration of the present invention is high.
　図１は、本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例１）に係る平面図である。 FIG. 1 is a plan view according to one embodiment (Example 1) of a sensor element used in the thermal sensor device of the present invention.
　センサ素子１は、フォトリソグラフィーを利用した半導体微細加工技術やエッチング技術を用いて形成される。センサ素子（熱式センサ素子）１は、単結晶シリコンで形成された基板２を有している。基板２は、空洞部３が形成され、空洞部３を絶縁膜によって覆うことにより構成される薄膜部４を備えている。薄膜部４には、発熱体としての検出ヒータ５及び補助ヒータ６が敷設される。検出ヒータ５及び補助ヒータ６は、薄膜部４の平面（膜面）に沿って延在し、複数の折り返し部を有する抵抗パターンとして形成される。 The sensor element 1 is formed using a semiconductor microfabrication technique or an etching technique using photolithography. A sensor element (thermal sensor element) 1 has a substrate 2 formed of single crystal silicon. The substrate 2 includes a thin film portion 4 formed with a cavity portion 3 formed by covering the cavity portion 3 with an insulating film. The thin film portion 4 is provided with a detection heater 5 and an auxiliary heater 6 as heating elements. The detection heater 5 and the auxiliary heater 6 are formed as a resistance pattern extending along the plane (film surface) of the thin film portion 4 and having a plurality of folded portions.
　検出ヒータ５は湿度の検出に用いられる。本実施例の場合、検出ヒータ５は例えば５００℃程度の一定温度に制御される。検出ヒータ５の放熱量は雰囲気の湿度に依存して変化し、検出ヒータ５を５００℃に保つために必要な電力が変化する。この電力変化を測定することで湿度を検出できる。 Detecting heater 5 is used for humidity detection. In this embodiment, the detection heater 5 is controlled to a constant temperature of about 500 ° C., for example. The amount of heat released from the detection heater 5 changes depending on the humidity of the atmosphere, and the power required to keep the detection heater 5 at 500 ° C. changes. Humidity can be detected by measuring this power change.
　検出ヒータ５の材料としては、高温において安定で、且つ抵抗温度係数が高い材料が好適である。例えば、白金（Ｐｔ）、タンタル（Ｔａ）、モリブデン（Ｍｏ）、タングステン（Ｗ）等の金属材料が好適である。 The material of the detection heater 5 is preferably a material that is stable at a high temperature and has a high resistance temperature coefficient. For example, metal materials such as platinum (Pt), tantalum (Ta), molybdenum (Mo), and tungsten (W) are suitable.
　補助ヒータ６は、検出ヒータ５を取り囲むように敷設される。補助ヒータ６の材料としては、検出ヒータ５と同一材料により形成することができる。補助ヒータ６の役割は、検出ヒータ５の放熱量が環境温度に依存しないように、検出ヒータ５の周囲温度を一定に保持することである。補助ヒータ６の温度は、３００℃程度であり、検出ヒータ５の温度より低く設定される。 The auxiliary heater 6 is laid so as to surround the detection heater 5. The auxiliary heater 6 can be made of the same material as the detection heater 5. The role of the auxiliary heater 6 is to keep the ambient temperature of the detection heater 5 constant so that the heat radiation amount of the detection heater 5 does not depend on the environmental temperature. The temperature of the auxiliary heater 6 is about 300 ° C., and is set lower than the temperature of the detection heater 5.
　本実施例では、検出ヒータ５の周辺に検出ヒータ５の周囲を囲むように補助ヒータ６を設けた構成としているが、本発明の効果を得るために補助ヒータ６は必須ではない。補助ヒータ６は環境温度による温度依存性を補償するためのものであり、補助ヒータ６を有さない構成においても本発明の効果が得られる。 In this embodiment, the auxiliary heater 6 is provided around the detection heater 5 so as to surround the detection heater 5, but the auxiliary heater 6 is not essential in order to obtain the effect of the present invention. The auxiliary heater 6 is for compensating the temperature dependence due to the environmental temperature, and the effect of the present invention can be obtained even in a configuration without the auxiliary heater 6.
　基板２には、検出ヒータ５及び補助ヒータ６を外部の駆動回路と接続するために電極パッド７ａ～７ｄが設けられる。これらの電極パッド７ａ～７ｄには、アルミニウム（Ａｌ）等が選定される。 The substrate 2 is provided with electrode pads 7a to 7d for connecting the detection heater 5 and the auxiliary heater 6 to an external drive circuit. Aluminum (Al) or the like is selected for these electrode pads 7a to 7d.
　図２は、本発明の熱式センサ装置の駆動回路（回路構成）の一実施例を示す回路図である。なお、熱式センサ装置１００は、センサ素子１を含む駆動回路全体である。実施例１で説明する熱式センサ装置１００は、他の実施例にも適用される。 FIG. 2 is a circuit diagram showing an embodiment of a drive circuit (circuit configuration) of the thermal sensor device of the present invention. The thermal sensor device 100 is the entire drive circuit including the sensor element 1. The thermal sensor device 100 described in the first embodiment is also applied to other embodiments.
　駆動回路は、検出ヒータ５及び補助ヒータ６と、検出ヒータ５を加熱制御するブリッジ回路（第１ブリッジ回路）ＢＣ１と、補助ヒータ６を加熱制御するブリッジ回路（第２ブリッジ回路）ＢＣ２と、から成る。 The drive circuit includes a detection heater 5 and an auxiliary heater 6, a bridge circuit (first bridge circuit) BC1 that controls heating of the detection heater 5, and a bridge circuit (second bridge circuit) BC2 that controls heating of the auxiliary heater 6. Become.
　検出ヒータ５が含まれるブリッジ回路ＢＣ１は、検出ヒータ５に抵抗８ａを接続した直列回路と、抵抗８ｂと抵抗８ｃとを接続した直列回路と、を並列接続した構成である。検出ヒータ５と抵抗８ａとの接続部（中間部）の電位（第１中間電位）と、抵抗８ｂと抵抗８ｃとの接続部（中間部）の電位（第２中間電位）とは差動増幅器９ａに入力される。差動増幅器９ａは、入力電圧の差（第１中間電位と第２中間電位との電位差）に応じた電圧、または電流を出力する。差動増幅器９ａの出力はブリッジ回路ＢＣ１の検出ヒータ５と抵抗８ｂとの間に接続され、検出ヒータ５の加熱電流としてフィードバックされる。検出ヒータ５が５００℃となる抵抗値でブリッジ回路ＢＣ１がバランスするように抵抗８ａ～８ｃを選定することにより、検出ヒータ５を一定温度に保持することができる。 The bridge circuit BC1 including the detection heater 5 has a configuration in which a series circuit in which the resistor 8a is connected to the detection heater 5 and a series circuit in which the resistor 8b and the resistor 8c are connected are connected in parallel. The potential of the connection portion (intermediate portion) between the detection heater 5 and the resistor 8a (first intermediate potential) and the potential of the connection portion (intermediate portion) between the resistors 8b and 8c (second intermediate potential) are a differential amplifier. It is input to 9a. The differential amplifier 9a outputs a voltage or current corresponding to the difference in input voltage (potential difference between the first intermediate potential and the second intermediate potential). The output of the differential amplifier 9a is connected between the detection heater 5 of the bridge circuit BC1 and the resistor 8b, and is fed back as a heating current of the detection heater 5. By selecting the resistors 8a to 8c so that the bridge circuit BC1 is balanced at a resistance value at which the detection heater 5 is 500 ° C., the detection heater 5 can be maintained at a constant temperature.
　補助ヒータ６が含まれるブリッジ回路ＢＣ２は、補助ヒータ６に抵抗１０ａを接続した直列回路と、抵抗１０ｂと抵抗１０ｃとを接続した直列回路と、を並列接続した構成である。補助ヒータ６と抵抗１０ａとの接続部（中間部）の電位（第３中間電位）と、抵抗１０ｂと抵抗１０ｃとの接続部（中間部）の電位（第４中間電位）とは差動増幅器９ｂに入力される。差動増幅器９ｂは、入力電圧の差（第３中間電位と第４中間電位との電位差）に応じた電圧、または電流を出力する。差動増幅器９ｂの出力はブリッジ回路ＢＣ２の補助ヒータ６と抵抗１０ｂとの間に接続され、補助ヒータ６の加熱電流としてフィードバックされる。補助ヒータ６が３００℃となる抵抗値でブリッジ回路ＢＣ２がバランスするように抵抗１０ａ～１０ｃを選定することにより、補助ヒータ６を一定温度に保持することができる。 The bridge circuit BC2 including the auxiliary heater 6 has a configuration in which a series circuit in which the resistor 10a is connected to the auxiliary heater 6 and a series circuit in which the resistor 10b and the resistor 10c are connected are connected in parallel. The potential (third intermediate potential) at the connection portion (intermediate portion) between the auxiliary heater 6 and the resistor 10a and the potential (fourth intermediate potential) at the connection portion (intermediate portion) between the resistors 10b and 10c are the differential amplifier. 9b. The differential amplifier 9b outputs a voltage or current corresponding to the difference in input voltage (potential difference between the third intermediate potential and the fourth intermediate potential). The output of the differential amplifier 9b is connected between the auxiliary heater 6 of the bridge circuit BC2 and the resistor 10b, and is fed back as a heating current of the auxiliary heater 6. By selecting the resistors 10a to 10c so that the bridge circuit BC2 is balanced at a resistance value at which the auxiliary heater 6 is 300 ° C., the auxiliary heater 6 can be maintained at a constant temperature.
　以下、上記のような熱式センサ装置１００における検出ヒータ５の抵抗変化について説明する。 Hereinafter, the resistance change of the detection heater 5 in the thermal sensor device 100 as described above will be described.
　検出ヒータ５は金属材料で形成し、その周囲の絶縁膜は酸化シリコンや窒化シリコンで形成される。金属材料は線膨張係数が大きいため高温に加熱すると、周辺の絶縁膜により膨張が妨げられ、検出ヒータ５に圧縮応力が働く。圧縮応力が小さければ検出ヒータ５に応力が加わっても弾性変形となるため、冷却すれば検出ヒータ５は元の形状に戻る。しかし、高温に加熱することによって熱ストレスが大きくなると、検出ヒータ５は弾性変形の領域を越えて塑性変形となり、残留応力が蓄積する。これにより、検出ヒータ５の抵抗値が徐々に変化し、計測精度に影響を与える。 The detection heater 5 is made of a metal material, and the surrounding insulating film is made of silicon oxide or silicon nitride. Since the metal material has a large linear expansion coefficient, when heated to a high temperature, expansion is hindered by the surrounding insulating film, and compressive stress acts on the detection heater 5. If the compressive stress is small, the detection heater 5 is elastically deformed even when stress is applied to it. Therefore, the detection heater 5 returns to its original shape when cooled. However, when the thermal stress increases by heating to a high temperature, the detection heater 5 becomes plastically deformed beyond the elastic deformation region, and residual stress accumulates. As a result, the resistance value of the detection heater 5 gradually changes and affects the measurement accuracy.
　加熱による検出ヒータ５に加わる応力を低減するためには、検出ヒータ５と周囲の絶縁膜との膨張係数の差を小さくすることが好ましい。絶縁膜は圧縮性応力を有する酸化シリコン膜と、引張性応力を有する窒化シリコン膜の積層によって形成される。検出ヒータ５に用いる金属材料は圧縮性であることから、絶縁膜は検出ヒータと同じ圧縮性応力を有する酸化シリコンによって形成することが望ましい。 In order to reduce the stress applied to the detection heater 5 due to heating, it is preferable to reduce the difference in expansion coefficient between the detection heater 5 and the surrounding insulating film. The insulating film is formed by stacking a silicon oxide film having compressive stress and a silicon nitride film having tensile stress. Since the metal material used for the detection heater 5 is compressive, it is desirable that the insulating film be formed of silicon oxide having the same compressive stress as the detection heater.
　しかしながら、絶縁膜を構成する薄膜部の圧縮性を増加させると、薄膜部に反り変形が生じる。図３に薄膜部４が引張性である場合と圧縮性である場合の反り形状を示す。 However, when the compressibility of the thin film portion constituting the insulating film is increased, the thin film portion is warped and deformed. FIG. 3 shows the warp shape when the thin film portion 4 is tensile and compressive.
　図３Ａは、熱式センサ装置に用いられるセンサ素子の変形を概念的に示す断面図であり、薄膜部を形成する積層膜の合成応力が引張性となるように膜厚を設定した場合の、薄膜部の断面形状を示す図である。 FIG. 3A is a cross-sectional view conceptually showing deformation of a sensor element used in a thermal sensor device, where the film thickness is set so that the composite stress of the laminated film forming the thin film portion becomes tensile. It is a figure which shows the cross-sectional shape of a thin film part.
　図３Ａでは、酸化シリコン膜と窒化シリコン膜を積層して薄膜部４を形成している。酸化シリコン膜及び窒化シリコン膜の合成応力は引張性となるように、各膜厚が設定されている。この場合、図３Ａに示すように、薄膜部４は平坦な形状となり良好に製造することができる。 In FIG. 3A, a thin film portion 4 is formed by laminating a silicon oxide film and a silicon nitride film. Each film thickness is set so that the combined stress of the silicon oxide film and the silicon nitride film becomes tensile. In this case, as shown to FIG. 3A, the thin film part 4 becomes a flat shape and can be manufactured favorably.
　図３Ｂは、熱式センサ装置に用いられるセンサ素子の変形を概念的に示す断面図であり、薄膜部を形成する積層膜の合成応力が圧縮性となるように膜厚を設定した場合の、薄膜部の断面形状を示す図である。 FIG. 3B is a cross-sectional view conceptually showing deformation of the sensor element used in the thermal sensor device, and when the film thickness is set so that the combined stress of the laminated film forming the thin film portion becomes compressive, It is a figure which shows the cross-sectional shape of a thin film part.
　図３Ｂでは、酸化シリコン膜及び窒化シリコン膜の合成応力は引張性となるように、各膜厚が設定されている。薄膜部４の酸化シリコン膜の比率を増して圧縮性とした場合、図３Ｂに示すように、薄膜部４に撓みが生じ機械的強度が低下する。 In FIG. 3B, each film thickness is set so that the combined stress of the silicon oxide film and the silicon nitride film is tensile. When the ratio of the silicon oxide film of the thin film portion 4 is increased to make it compressible, the thin film portion 4 is bent and mechanical strength is lowered as shown in FIG. 3B.
　上記の課題を解決する本発明の具体的実施例を、以下説明する。 Specific examples of the present invention that solve the above problems will be described below.
　図４Ａは、図１のIVA－IVA断面を示す断面図である。 FIG. 4A is a cross-sectional view showing the IVA-IVA cross section of FIG.
　センサ素子１は、単結晶シリコンから成る基板２の表面に、圧縮性絶縁膜１１ａが形成される。圧縮性絶縁膜１１ａは、主に酸化シリコン（ＳｉＯ２）から成り、熱酸化膜やＣＶＤ（Chemical Vapor Deposition）によって形成することができる。 In the sensor element 1, a compressible insulating film 11a is formed on the surface of a substrate 2 made of single crystal silicon. The compressible insulating film 11a is mainly made of silicon oxide (SiO 2), and can be formed by a thermal oxide film or CVD (Chemical Vapor Deposition).
　圧縮性絶縁膜１１ａ上には、引張性絶縁膜１２ａが形成される。引張性絶縁膜１２ａとしては、例えばＣＶＤ法により形成した窒化シリコン膜（Ｓｉ３Ｎ４）を用いることができる。引張性絶縁膜１２ａは、検出ヒータ５が形成される領域Ｂに対応する部分（検出ヒータ形成領域対応部分）１２ａ－１がエッチングにより部分的に取り除かれる。すなわち引張性絶縁膜１２ａは、引張性絶縁膜１２ａと検出ヒータ５とを基板２の平面（絶縁膜形成面）２ａ又は平面２ａに平行な仮想平面に投影した場合に、検出ヒータ５が形成される領域と重なる部分１２ａ－１が取り除かれている。 A tensile insulating film 12a is formed on the compressible insulating film 11a. As the tensile insulating film 12a, for example, a silicon nitride film (Si3N4) formed by a CVD method can be used. In the tensile insulating film 12a, a portion (detection heater forming region corresponding portion) 12a-1 corresponding to the region B where the detection heater 5 is formed is partially removed by etching. That is, the tensile insulating film 12a is formed when the tensile insulating film 12a and the detection heater 5 are projected on the plane (insulating film forming surface) 2a of the substrate 2 or a virtual plane parallel to the plane 2a. The portion 12a-1 that overlaps the region to be removed is removed.
　次に同様な方法で酸化シリコンからなる圧縮性絶縁膜１１ｂを形成する。圧縮性絶縁膜１１ｂの表面はＣＭＰ(Chemical mechanical polishing)などにより必要に応じて平坦化処理される。 Next, a compressible insulating film 11b made of silicon oxide is formed by the same method. The surface of the compressible insulating film 11b is planarized as necessary by CMP (Chemical-mechanical polishing) or the like.
　次に、金属膜をスパッタ法などにより形成してパターニングすることにより、検出ヒータ５及び補助ヒータ６を形成する。本実施例では金属膜として、高融点材料であり、且つ抵抗温度係数が高いモリブデン（Ｍｏ）を用いる。Ｍｏのほか白金、タンタル、タングステンなども用いることができる。 Next, the detection heater 5 and the auxiliary heater 6 are formed by forming and patterning a metal film by sputtering or the like. In this embodiment, molybdenum (Mo), which is a high melting point material and has a high resistance temperature coefficient, is used as the metal film. In addition to Mo, platinum, tantalum, tungsten and the like can also be used.
　最後に検出ヒータ５及び補助ヒータ６を保護するために、プラズマＣＶＤ法などを用いて酸化シリコンからなる圧縮性絶縁膜１１ｃを形成する。 Finally, in order to protect the detection heater 5 and the auxiliary heater 6, a compressive insulating film 11c made of silicon oxide is formed using a plasma CVD method or the like.
　検出ヒータ５及び補助ヒータ６が位置する基板２の部位は、水酸化カリウム（ＫＯＨ）などを用いて異方性エッチングされ、空洞部３が形成される。 The portion of the substrate 2 where the detection heater 5 and the auxiliary heater 6 are located is anisotropically etched using potassium hydroxide (KOH) or the like to form the cavity 3.
　前述したように、検出ヒータ５が形成される領域Ｂの絶縁膜の合成応力は圧縮性とする必要がある。そのため、本実施例では、引張性絶縁膜１２ａを部分的に除去することで、検出ヒータ５が形成される領域Ｂの圧縮性絶縁膜１１ａ，１１ｂ，１１ｃの比率を他の薄膜部４の領域Ａに比べて増加させている。つまり、絶縁膜１１ａ，１２ａ，１１ｂ，１１ｃで形成された薄膜部４の合成応力が部分的に圧縮性となる圧縮性領域Ｂが設けられ、この圧縮性領域Ｂに検出ヒータ５が配置されている。 As described above, the combined stress of the insulating film in the region B where the detection heater 5 is formed needs to be compressible. Therefore, in this embodiment, by partially removing the tensile insulating film 12a, the ratio of the compressive insulating films 11a, 11b, and 11c in the region B where the detection heater 5 is formed is changed to the region of the other thin film portion 4. Increased compared to A. That is, a compressive region B in which the combined stress of the thin film portion 4 formed of the insulating films 11a, 12a, 11b, and 11c is partially compressive is provided, and the detection heater 5 is disposed in the compressive region B. Yes.
　引張性絶縁膜１２ａを部分的に除去することで、検出ヒータ５が形成される領域Ｂは圧縮性（－σ）が強くなり、薄膜部４のその他の領域Ａは引張性（＋σ）となる。こうすることで、検出ヒータ５が形成された領域Ｂの膨張にともなう歪を、周囲の引張性を強くした領域Ａにより面方向において相殺することができ、薄膜部４を平坦な形状に製造することができる。 By partially removing the tensile insulating film 12a, the region B where the detection heater 5 is formed becomes stronger in compressibility (−σ), and the other region A of the thin film portion 4 becomes tensile (+ σ). . By doing so, the distortion caused by the expansion of the region B where the detection heater 5 is formed can be offset in the surface direction by the region A where the surrounding tensile property is strengthened, and the thin film portion 4 is manufactured in a flat shape. be able to.
　本実施例では、検出ヒータ５が形成された領域の引張性絶縁膜１２ａを除去しているが、補助ヒータ６が形成された領域は引張性絶縁膜１２ａを残した構造としている。この理由は、検出ヒータ５は温度が高く熱ストレスが大きくなるが、補助ヒータ６は検出ヒータ５に比べて温度が低く熱ストレスの影響が小さいためである。補助ヒータ６の温度を高く設定した場合は、補助ヒータ６が形成される領域においても引張性絶縁膜１１ｂを除去するなど、適宜除去範囲を調整することができる。 In this embodiment, the tensile insulating film 12a in the region where the detection heater 5 is formed is removed, but the region where the auxiliary heater 6 is formed has a structure in which the tensile insulating film 12a remains. This is because the detection heater 5 has a high temperature and a large thermal stress, but the auxiliary heater 6 has a lower temperature than the detection heater 5 and is less affected by the thermal stress. When the temperature of the auxiliary heater 6 is set high, the removal range can be adjusted as appropriate, for example, by removing the tensile insulating film 11b even in the region where the auxiliary heater 6 is formed.
　本実施例では、図４Ａに示したように、検出ヒータ５が配置された領域Ｂの引張性絶縁膜１２ａをすべて除去した構成としているが、検出ヒータ５の下部に部分的に引張性絶縁膜１２ａを残した構成としても良い。ここで、引張性絶縁膜１２ａを部分的に残すとは、引張性絶縁膜１２ａを２層以上設けた場合に、全ての引張性絶縁膜１２ａにおいて検出ヒータ形成領域対応部分１２ａ－１を除去する必要はなく、領域Ｂが圧縮性になっていれば、検出ヒータ形成領域対応部分１２ａ－１が除去されない引張性絶縁膜１２ａの層があってもよいことを意味する。或いは、引張性絶縁膜１２ａを部分的に残すとは、１層又は複数層からなる引張性絶縁膜１２ａ少なくとも１層の膜厚が薄くなるように、構成されることを意味する。 In this embodiment, as shown in FIG. 4A, the tensile insulating film 12a in the region B where the detection heater 5 is disposed is completely removed. However, the tensile insulating film is partially formed below the detection heater 5. It is good also as a structure which left 12a. Here, partially leaving the tensile insulating film 12a means that when two or more tensile insulating films 12a are provided, the detection heater forming region corresponding portion 12a-1 is removed from all the tensile insulating films 12a. It is not necessary, and if the region B is compressible, it means that there may be a layer of the tensile insulating film 12a from which the detection heater forming region corresponding portion 12a-1 is not removed. Alternatively, partially leaving the tensile insulating film 12a means that at least one tensile insulating film 12a composed of one layer or a plurality of layers is configured to be thin.
　検出ヒータ５の下部の引張性絶縁膜１２ａをどの程度除去するかは、熱式センサ装置１００が適用されるシステムの要求仕様に応じて設計可能である。また本実施例では、引張性絶縁膜１２ａを検出ヒータ５の領域Ｂ外の全面に形成した構成としているが、領域Ｂの外側において引張性絶縁膜１２ａが部分的に除去された部分があっても良い。つまり、検出ヒータ５の上層、下層の絶縁膜の圧縮化に伴う応力を吸収できる程度に引張性となっていれば、本発明の効果が得られる。 The degree to which the tensile insulating film 12a below the detection heater 5 is removed can be designed according to the required specifications of the system to which the thermal sensor device 100 is applied. In this embodiment, the tensile insulating film 12a is formed on the entire surface outside the region B of the detection heater 5, but there is a portion where the tensile insulating film 12a is partially removed outside the region B. Also good. That is, the effect of the present invention can be obtained as long as the tensile strength is high enough to absorb the stress accompanying the compression of the upper and lower insulating films of the detection heater 5.
　本実施例では、薄膜部４を形成する絶縁膜において、部分的に除去される引張性絶縁膜１２ａは圧縮性絶縁膜１１ａ、１１ｂ、１１ｃに挟まれるように形成している。この理由は、薄膜部４における中間層に近い層において部分的に除去された膜が介在する構成にすることで、薄膜部４の平面位置による反りモーメントの変化が小さくなり、より凹凸のない平坦な薄膜部４を形成することができるからである。 In this embodiment, in the insulating film forming the thin film portion 4, the tensile insulating film 12a to be partially removed is formed so as to be sandwiched between the compressive insulating films 11a, 11b, and 11c. The reason for this is that, by adopting a configuration in which a partially removed film is interposed in a layer close to the intermediate layer in the thin film portion 4, the change in the warping moment due to the planar position of the thin film portion 4 is reduced, and the flatness without unevenness is reduced. This is because the thin film portion 4 can be formed.
　本実施例では、検出ヒータ５や補助ヒータ６などの発熱体の下層側に引張性絶縁膜１２ａを形成した構造としているが、これらの発熱体の上層側に引張性絶縁膜１２ａを形成して、発熱体が形成される領域の引張性絶縁膜１２ａを部分的に除去した構造としても良い。この場合、プラズマＣＶＤ法などを用いた窒化シリコン膜を用いることができる。 In this embodiment, the tensile insulating film 12a is formed on the lower layer side of the heating elements such as the detection heater 5 and the auxiliary heater 6, but the tensile insulating film 12a is formed on the upper layer side of these heating elements. A structure in which the tensile insulating film 12a in the region where the heating element is formed is partially removed may be employed. In this case, a silicon nitride film using a plasma CVD method or the like can be used.
　本実施例では、薄膜部４を形成する引張性絶縁膜１２ａの材料として窒化シリコン膜を用いたが、窒化シリコン膜に限定されるものではなく、引張応力を備えた材料であれば同様な構成にすることができる。例えば窒化アルミニウムなども引張性絶縁膜１２ａの材料として用いることができる。 In this embodiment, a silicon nitride film is used as the material of the tensile insulating film 12a forming the thin film portion 4. However, the material is not limited to the silicon nitride film, and the same configuration is possible as long as the material has tensile stress. Can be. For example, aluminum nitride or the like can be used as a material for the tensile insulating film 12a.
　窒化シリコン膜と酸化シリコン膜の積層膜で形成した薄膜部４の内部応力は温度によって変化する。 The internal stress of the thin film portion 4 formed by the laminated film of the silicon nitride film and the silicon oxide film varies depending on the temperature.
　図４Ｂは、薄膜部４、検出ヒータ５、引張性領域Ａ及び圧縮性領域Ｂを基板２の基板面（絶縁膜形成面）に平行な仮想平面に投影した図である。 FIG. 4B is a diagram in which the thin film portion 4, the detection heater 5, the tensile region A, and the compressive region B are projected on a virtual plane parallel to the substrate surface (insulating film forming surface) of the substrate 2.
　（ａ）では、検出ヒータ５が位置する領域Ｂの引張性絶縁膜１２ａは、方形に除去される。引張性絶縁膜１２ａを方形に除去すると、角部において応力集中が発生しやすくなる。このため、（ｂ）や（ｃ）のように、除去する形状（領域Ｂの形状）を多角形や円形とすることで、角部における応力集中を低減し、薄膜部４の強度低下を抑制できる。 (A) The tensile insulating film 12a in the region B where the detection heater 5 is located is removed in a square shape. When the tensile insulating film 12a is removed in a square shape, stress concentration tends to occur at the corners. For this reason, as shown in (b) and (c), the shape to be removed (the shape of the region B) is a polygon or a circle, thereby reducing the stress concentration at the corner and suppressing the strength reduction of the thin film portion 4. it can.
　なお、図４Ｂに示す領域Ｂの形状は、矛盾しない範囲内で、後述する実施例に適用できる。 It should be noted that the shape of the region B shown in FIG. 4B can be applied to the embodiments described later within a consistent range.
　図５は、本発明に係るセンサ素子の一実施例における応力の温度依存性を示す図である。図５では、単結晶シリコン基板２に形成した薄膜部４の温度と内部応力との関係を示している。 FIG. 5 is a diagram showing the temperature dependence of stress in one embodiment of the sensor element according to the present invention. FIG. 5 shows the relationship between the temperature of the thin film portion 4 formed on the single crystal silicon substrate 2 and the internal stress.
　図５に示すように単結晶シリコンで形成した基板２に形成した薄膜部４は、温度の上昇に伴い引張応力（＋σ）となり、温度が低下すると圧縮応力（－σ）が強くなる特性がる。引張応力となる高温域であれば薄膜部４は平坦となるが、温度が低下すると圧縮性が強くなり薄膜部４に反りが生じる。 As shown in FIG. 5, the thin film portion 4 formed on the substrate 2 made of single crystal silicon has a characteristic that the tensile stress (+ σ) increases as the temperature increases, and the compressive stress (−σ) increases as the temperature decreases. . The thin film portion 4 is flat if it is in a high temperature range where tensile stress is applied. However, when the temperature is lowered, the compressibility becomes strong and the thin film portion 4 is warped.
　図５に示した破線Ａは低温側（室温）において引張性を強めた薄膜構造の内部応力の温度特性であり、図４に示した本実施例における領域Ａの薄膜構造に相当する。領域Ａでの薄膜構造の場合、低温側および高温側において引張性を維持している。 The broken line A shown in FIG. 5 is the temperature characteristic of the internal stress of the thin film structure with enhanced tensile properties on the low temperature side (room temperature), and corresponds to the thin film structure in the region A in this embodiment shown in FIG. In the case of the thin film structure in the region A, the tensile property is maintained on the low temperature side and the high temperature side.
　実線Ｂは圧縮性を強めた薄膜構造の内部応力の温度特性であり、図４に示した本実施例における領域Ｂの薄膜構造に相当する。領域Ｂでの薄膜構造の場合、高温側で引張性、低温側（室温）で圧縮性となる。 The solid line B is the temperature characteristic of the internal stress of the thin film structure with enhanced compressibility, and corresponds to the thin film structure of the region B in this embodiment shown in FIG. In the case of the thin film structure in the region B, it becomes tensile on the high temperature side and compressible on the low temperature side (room temperature).
　本実施例の薄膜部４は、上記の破線Ａ及び実線Ｂの特性を持つ絶縁膜を組み合わせた構成である。低温側（室温）において圧縮性となる絶縁膜と引張性となる絶縁膜が互いにキャンセルしあうことで空洞部全体の応力が引張性を維持できる構成になる。 The thin film portion 4 of this embodiment has a configuration in which the insulating films having the characteristics of the broken line A and the solid line B are combined. By compressing the insulating film that becomes compressive and the insulating film that becomes tensile on the low temperature side (room temperature), the stress of the entire cavity portion can maintain the tensile property.
　［実施例２］
　図６は、本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例２）に係る断面図である。実施例１と同様な構成には、同じ符号を付し、説明を省略する。本実施例のセンサ素子２０について、以下説明する。 [Example 2]
FIG. 6 is a cross-sectional view according to one embodiment (Example 2) of a sensor element used in the thermal sensor device of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. The sensor element 20 of the present embodiment will be described below.
　本実施例では、３層の窒化シリコン膜Ｓｉ３Ｎ４を設けた構成について説明する。 In this embodiment, a configuration in which a three-layer silicon nitride film Si 3 N 4 is provided will be described.
　単結晶シリコンから成る基板２の表面に圧縮性絶縁膜２１ａを形成する。圧縮性絶縁膜２１ａは、主に酸化シリコン（ＳｉＯ２）からなり、熱酸化膜やＣＶＤ（Chemical Vapor Deposition）によって形成することができる。 Compressive insulating film 21a is formed on the surface of substrate 2 made of single crystal silicon. The compressible insulating film 21a is mainly made of silicon oxide (SiO2), and can be formed by a thermal oxide film or CVD (Chemical Vapor Deposition).
　圧縮性絶縁膜２１ａ上には、引張性絶縁膜２２ａが形成される。引張性絶縁膜２２ａとしては、例えばＣＶＤ法により形成した窒化シリコン膜（Ｓｉ３Ｎ４）を用いることができる。引張性絶縁膜２２ａは空洞部３上を完全に覆うように均一な膜厚で形成している。 A tensile insulating film 22a is formed on the compressible insulating film 21a. As the tensile insulating film 22a, for example, a silicon nitride film (Si3N4) formed by a CVD method can be used. The tensile insulating film 22a is formed with a uniform film thickness so as to completely cover the cavity 3.
　引張性絶縁膜２２ａ上には同様な手法で酸化シリコンを材料とした圧縮性絶縁膜２１ｂが形成される。 A compressible insulating film 21b made of silicon oxide is formed on the tensile insulating film 22a in the same manner.
　圧縮性絶縁膜２１ｂ上には窒化シリコンからなる引張性絶縁膜２２ｂが形成される。引張性絶縁膜２２ｂは、検出ヒータ５が形成される領域Ｂに対応する部分（検出ヒータ形成領域対応部分）１２ａ－１がエッチングにより部分的に取り除かれる。 A tensile insulating film 22b made of silicon nitride is formed on the compressible insulating film 21b. In the tensile insulating film 22b, the portion corresponding to the region B where the detection heater 5 is formed (detection heater formation region corresponding portion) 12a-1 is partially removed by etching.
　次に同様な方法で酸化シリコンからなる圧縮性絶縁膜２１ｃを形成する。圧縮性絶縁膜２１ｃの表面はＣＭＰ(Chemical mechanical polishing)などにより必要に応じて平坦化処理される。 Next, a compressible insulating film 21c made of silicon oxide is formed by the same method. The surface of the compressible insulating film 21c is planarized as necessary by CMP (Chemical mechanical polishing) or the like.
　次に、金属膜をスパッタ法などにより形成しパターニングすることにより検出ヒータ５と補助ヒータ６を形成する。本実施例では金属膜として、高融点材料であり抵抗温度係数が高いモリブデン（Ｍｏ）を用いる。 Next, the detection heater 5 and the auxiliary heater 6 are formed by forming and patterning a metal film by sputtering or the like. In this embodiment, molybdenum (Mo), which is a high melting point material and has a high resistance temperature coefficient, is used as the metal film.
　次に検出ヒータ５および補助ヒータ６を保護するために、プラズマＣＶＤ法などを用いて酸化シリコンからなる圧縮性絶縁膜２１ｄを形成する。 Next, in order to protect the detection heater 5 and the auxiliary heater 6, a compressive insulating film 21d made of silicon oxide is formed using a plasma CVD method or the like.
　圧縮性絶縁膜２１ｄ上には引張性絶縁膜２２ｃを形成する。引張性絶縁膜２２ｃとしては、プラズマＣＶＤ法により形成した窒化シリコンを用いることができる。 A tensile insulating film 22c is formed on the compressible insulating film 21d. As the tensile insulating film 22c, silicon nitride formed by a plasma CVD method can be used.
　最後に、圧縮性絶縁膜２１ｅを同様な手法で形成する。 Finally, the compressible insulating film 21e is formed by the same method.
　検出ヒータ５及び補助ヒータ６が位置する基板２には、水酸化カリウム（ＫＯＨ）などを用いて異方性エッチングすることにより空洞部３が形成される。 The cavity 3 is formed in the substrate 2 on which the detection heater 5 and the auxiliary heater 6 are located by anisotropic etching using potassium hydroxide (KOH) or the like.
　本実施例の圧縮性絶縁膜２１ｂ、引張性絶縁膜２２ｂ、圧縮性絶縁膜２１ｃ及び圧縮性絶縁膜２１ｄは、実施例１の圧縮性絶縁膜１１ａ、引張性絶縁膜１２ａ、圧縮性絶縁膜１１ｂ及び圧縮性絶縁膜１１ｃに対応する。さらに本実施例では、引張性絶縁膜２２ａ及び引張性絶縁膜２２ｃが追加されるために、最下層の圧縮性絶縁膜２１ａ及び最上層の圧縮性絶縁膜２１ｅが追加される。 The compressible insulating film 21b, the tensile insulating film 22b, the compressible insulating film 21c, and the compressible insulating film 21d of the present embodiment are the same as the compressive insulating film 11a, the tensile insulating film 12a, and the compressible insulating film 11b of the first embodiment. And the compressive insulating film 11c. Further, in this embodiment, since the tensile insulating film 22a and the tensile insulating film 22c are added, the lowermost compressive insulating film 21a and the uppermost compressive insulating film 21e are added.
　本実施例においても、引張性絶縁膜１２ｂが部分的に除去されることで、検出ヒータ５が形成された領域Ｂが他の領域Ａに比べ圧縮性を強めた構成となる。つまり、本実施例においても、検出ヒータ５が形成される領域Ｂの圧縮性絶縁膜（酸化シリコン膜）の比率を他の部分Ａに比べ増加させている。引張性絶縁膜１２ｂを部分的に除去することで、検出ヒータ５が形成される領域Ｂは圧縮性（－σ）が強くなり、薄膜部４のその他の領域Ａは引張性（＋σ）が強められている。すなわち、空洞部３に設けられた薄膜部４内に、圧縮性領域（圧縮性薄膜部）Ｂと引張性領域（引張性薄膜部）Ａとが形成され、圧縮性領域（圧縮性薄膜部）Ｂに検出ヒータ５が配置されている。こうすることで、検出ヒータ５が形成された薄膜部４の絶縁膜の膨張にともなう形状変化を、周囲の引張性を強くした絶縁膜により相殺することができ、薄膜部４を平坦な形状とすることができる。 Also in the present embodiment, the tensile insulating film 12b is partially removed, so that the region B where the detection heater 5 is formed has a configuration in which the compressibility is enhanced as compared with the other regions A. That is, also in this embodiment, the ratio of the compressible insulating film (silicon oxide film) in the region B where the detection heater 5 is formed is increased as compared with the other part A. By partially removing the tensile insulating film 12b, the region B where the detection heater 5 is formed has a higher compressibility (−σ), and the other region A of the thin film portion 4 has a higher tensile property (+ σ). It has been. That is, a compressible region (compressible thin film portion) B and a tensile region (tensile thin film portion) A are formed in the thin film portion 4 provided in the cavity portion 3, and the compressive region (compressible thin film portion). A detection heater 5 is arranged at B. By doing so, the shape change accompanying the expansion of the insulating film of the thin film portion 4 on which the detection heater 5 is formed can be offset by the surrounding insulating film having enhanced tensile properties, so that the thin film portion 4 has a flat shape. can do.
　本実施例においては、空洞部３上の領域を完全に覆う引張性絶縁膜２２ａと引張性絶縁膜２２ｃを備える構成とした。また、検出ヒータ５は、上層側の引張性絶縁膜２２ｃと下層側の引張性絶縁膜２２ａとの間に介在する構成とした。引張性絶縁膜２２ａ，２２ｃは窒化シリコンで形成されるため外部から浸入する水分や酸素などを遮断する効果があり、これにより、検出ヒータ５を酸化や腐食から保護する効果を高めることができる。 In the present embodiment, the tensile insulating film 22a and the tensile insulating film 22c that completely cover the region on the cavity 3 are provided. Further, the detection heater 5 is configured to be interposed between the upper tensile insulating film 22c and the lower tensile insulating film 22a. Since the tensile insulating films 22a and 22c are formed of silicon nitride, the tensile insulating films 22a and 22c have an effect of blocking moisture and oxygen entering from the outside, thereby enhancing the effect of protecting the detection heater 5 from oxidation and corrosion.
　本実施例においては、引張性絶縁膜２２ａ，２２ｃと、引張性絶縁膜２２ａ，２２ｃを設けるために追加された圧縮性絶縁膜２１ａ及び圧縮性絶縁膜２１ｅに係る構成が実施例１と相違しており、それ以外の構成は、実施例１と同様に構成することができる。 In the present embodiment, the structures relating to the tensile insulating films 22a and 22c and the compressible insulating film 21a and the compressible insulating film 21e added to provide the tensile insulating films 22a and 22c are different from the first embodiment. Other configurations can be configured in the same manner as in the first embodiment.
　また本実施例では、中間層に位置する引張性絶縁膜２２ｂを部分的に除去した窒化シリコン膜で形成している。この場合、薄膜部４の積層方向の中心に近い膜を部分的に除去した構成となるため、薄膜部４の平面位置における反りモーメントの変化が小さくなり、より凹凸のない平坦な薄膜を形成することができる。 In this embodiment, the silicon nitride film is formed by partially removing the tensile insulating film 22b located in the intermediate layer. In this case, since the film close to the center in the stacking direction of the thin film portion 4 is partially removed, the change in the warping moment at the planar position of the thin film portion 4 is reduced, and a flat thin film without unevenness is formed. be able to.
　［実施例３］
　図７Ａは、本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例３）に係る断面図である。 [Example 3]
FIG. 7A is a cross-sectional view according to one embodiment (third embodiment) of a sensor element used in the thermal sensor device of the present invention.
　本実施例は、実施例２に対してさらに構成を追加したものであり、実施例２と異なる構成及び効果について説明する。実施例１及び実施例２と同様な構成については、実施例１及び実施例２と同じ符号を付し、説明を省略する。また同じ符号を付した構成について、他の実施例と異なる部分については、その都度説明する。なお補助ヒータ６は必須の構成ではないため、図７では記載を省略しているが、実施例１及び実施例２と同様に補助ヒータ６を設けてもよい。本実施例のセンサ素子３０について、以下説明する。 In this embodiment, a configuration is further added to the second embodiment, and the configuration and effects different from the second embodiment will be described. Components similar to those in the first and second embodiments are denoted by the same reference numerals as those in the first and second embodiments, and the description thereof is omitted. Moreover, about the structure which attached | subjected the same code | symbol, a different part from another Example is demonstrated each time. Since the auxiliary heater 6 is not an essential configuration, the description is omitted in FIG. 7, but the auxiliary heater 6 may be provided as in the first and second embodiments. The sensor element 30 of the present embodiment will be described below.
　引張性絶縁膜２２ｂは、検出ヒータ５の領域において部分的に除去される。本実施例では、薄膜部４の引張性絶縁膜２２ｂが除去された領域Ｂと、引張性絶縁膜２２ｂが形成された領域Ａとの間に緩衝領域Ｃを設けている。緩衝領域Ｃは、領域Ａと領域Ｂとの境界における急激な膜質変化を緩和するものであり、検出ヒータ５に近づくに従い引張性絶縁膜２２ｂを徐々に除去した構造を備えている。具体的には、緩衝領域Ｃにおいて、引張性絶縁膜１２ｂにスリットや孔を設けることで形成することができる。例えば、スリットの幅や孔の径又は幅を変えたり、スリットや孔の間隔を変えたりすることで、急激な膜質変化を緩和する。 The tensile insulating film 22b is partially removed in the region of the detection heater 5. In this embodiment, a buffer region C is provided between the region B where the tensile insulating film 22b of the thin film portion 4 is removed and the region A where the tensile insulating film 22b is formed. The buffer region C relaxes a rapid film quality change at the boundary between the region A and the region B, and has a structure in which the tensile insulating film 22b is gradually removed as the detection heater 5 is approached. Specifically, the buffer region C can be formed by providing slits or holes in the tensile insulating film 12b. For example, a rapid change in film quality is alleviated by changing the width of the slit, the diameter or width of the hole, or changing the interval between the slit and the hole.
　上記構成による効果について説明する。熱式センサ装置１００が使用されるシステム環境では、圧力変動や粒子衝撃などによりセンサ素子３０の薄膜部４に外力が働く場合がある。薄膜部４に外力が働くと絶縁膜に応力が生じる。特に、薄膜部４上において膜質が変化する箇所は撓みによる応力集中により破壊しやすくなる。これに対して、領域Ａと領域Ｂとの間の膜質を徐々に変化させることで応力集中を緩和し、薄膜部４の強度低下を抑制することができる。 The effect of the above configuration will be described. In a system environment where the thermal sensor device 100 is used, an external force may act on the thin film portion 4 of the sensor element 30 due to pressure fluctuation or particle impact. When an external force acts on the thin film portion 4, stress is generated in the insulating film. In particular, the location where the film quality changes on the thin film portion 4 is likely to break due to stress concentration due to bending. In contrast, by gradually changing the film quality between the region A and the region B, the stress concentration can be relaxed and the strength reduction of the thin film portion 4 can be suppressed.
　図７Ｂは、薄膜部４、検出ヒータ５、引張性領域Ａ、圧縮性領域Ｂ及び緩衝領域Ｃを基板２の基板面（絶縁膜形成面）に平行な仮想平面に投影した図である。 FIG. 7B is a diagram in which the thin film portion 4, the detection heater 5, the tensile region A, the compressive region B, and the buffer region C are projected on a virtual plane parallel to the substrate surface (insulating film forming surface) of the substrate 2.
　緩衝領域Ｃを構成するスリットや孔の形状の具体例として、図７Ｂに示すような形状が考えられる。しかしスリットや孔の形状は、図７Ｂに示す形状以外の形状であってもよい。図７Ｂに示すように、領域Ａと領域Ｂとの境界にスリット又は孔により引張性絶縁膜を除去した緩衝領域Ｃを設けることによって、領域Ａと領域Ｂとの境界における応力集中を緩和できる。 As a specific example of the shape of the slit or hole constituting the buffer region C, a shape as shown in FIG. 7B can be considered. However, the shape of the slit or hole may be other than the shape shown in FIG. 7B. As shown in FIG. 7B, the stress concentration at the boundary between the region A and the region B can be reduced by providing the buffer region C from which the tensile insulating film is removed by a slit or a hole at the boundary between the region A and the region B.
　なお、図７Ｂに示す緩衝領域Ｃの形状は、矛盾しない範囲内で、後述する実施例に適用できる。特に、図４Ｂで説明した領域Ｂの形状（ｂ），（ｃ）と組み合わせることで、応力集中を緩和する効果が向上する。 It should be noted that the shape of the buffer region C shown in FIG. 7B can be applied to the embodiments described later within a consistent range. In particular, by combining with the shapes (b) and (c) of the region B described with reference to FIG. 4B, the effect of relaxing the stress concentration is improved.
　［実施例４］
　図８は、本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例４）に係る断面図である。 [Example 4]
FIG. 8 is a cross-sectional view according to an embodiment (embodiment 4) of a sensor element used in the thermal sensor device of the present invention.
　本実施例は、実施例２を変更したものであり、実施例２と異なる構成及び効果について説明する。実施例１～３と同様な構成については、実施例１～３と同じ符号を付し、説明を省略する。また同じ符号を付した構成について、他の実施例と異なる部分については、その都度説明する。なお補助ヒータ６は必須の構成ではないため、図８では記載を省略しているが、実施例１及び実施例２と同様に補助ヒータ６を設けてもよい。本実施例のセンサ素子４０について、以下説明する。 The present embodiment is a modification of the second embodiment, and the configuration and effect different from the second embodiment will be described. The same configurations as those in the first to third embodiments are denoted by the same reference numerals as those in the first to third embodiments, and the description thereof is omitted. Moreover, about the structure which attached | subjected the same code | symbol, a different part from another Example is demonstrated each time. Since the auxiliary heater 6 is not an essential configuration, the description thereof is omitted in FIG. 8, but the auxiliary heater 6 may be provided as in the first and second embodiments. The sensor element 40 of the present embodiment will be described below.
　本実施例は、検出ヒータ５が比較的大きなパターンである場合に有効な構成である。本実施例では、薄膜部４の検出ヒータ５が形成された領域Ｂにおいて、引張性絶縁膜２２ｂが一部残されている。すなわち本実施例では、引張性絶縁膜２２ｂの構成が一部で実施例２と相違している。検出ヒータ５の形成領域が広くなると、圧縮性とすべき領域も広がる。そうすると、検出ヒータ５の周辺の領域Ａが狭くなり、検出ヒータ５の領域Ｂの圧縮性の歪を十分に吸収しきれなくなる。 This embodiment is effective when the detection heater 5 has a relatively large pattern. In this embodiment, a part of the tensile insulating film 22b is left in the region B where the detection heater 5 of the thin film portion 4 is formed. That is, in this embodiment, the structure of the tensile insulating film 22b is partially different from that of the second embodiment. If the formation area of the detection heater 5 is widened, the area to be compressible is also widened. As a result, the area A around the detection heater 5 becomes narrow, and the compressive strain in the area B of the detection heater 5 cannot be sufficiently absorbed.
　そこで本実施例では、検出ヒータ５の領域Ｂにおいて、検出ヒータ５がパターニングされた直下を除いて引張性絶縁膜１２ｂを設けている。言い換えれば、検出ヒータ５がパターニングされた直下の引張性絶縁膜１２ｂを除去している。つまり、薄膜部４を上面から見たときに検出ヒータ５と引張性絶縁膜１２ｂとが重ならないようにしている。すなわち、検出ヒータ５と引張性絶縁膜１２ｂとを図１と同様な平面図に投影した場合に、検出ヒータ５を構成する金属パターンの間に窒化シリコンで構成される引張性絶縁膜１２ｂが設けられている。 Therefore, in this embodiment, the tensile insulating film 12b is provided in the region B of the detection heater 5 except for the portion immediately below where the detection heater 5 is patterned. In other words, the tensile insulating film 12b just under the patterning of the detection heater 5 is removed. That is, the detection heater 5 and the tensile insulating film 12b do not overlap when the thin film portion 4 is viewed from above. That is, when the detection heater 5 and the tensile insulating film 12b are projected on a plan view similar to FIG. 1, the tensile insulating film 12b made of silicon nitride is provided between the metal patterns constituting the detection heater 5. It has been.
　本実施例の構成により、検出ヒータ５が形成された部位の薄膜部４の圧縮性を増加させると共に、圧縮化に伴う歪を吸収する領域Ｃを確保することができる。 With the configuration of this embodiment, it is possible to increase the compressibility of the thin film portion 4 at the site where the detection heater 5 is formed, and to secure a region C that absorbs strain accompanying compression.
　［実施例５］
　図９は、本発明の熱式センサ装置に用いられるセンサ素子の一実施例（実施例５）に係る断面図である。 [Example 5]
FIG. 9 is a cross-sectional view according to one embodiment (Example 5) of the sensor element used in the thermal sensor device of the present invention.
　本実施例では、圧縮性絶縁膜となる酸化膜の圧膜化により、検出ヒータ５が形成された領域Ｂの圧縮性を他の領域Ａに比べて強める。実施例１～４と同様な構成については、実施例１～４と同じ符号を付し、説明を省略する。また同じ符号を付した構成について、他の実施例と異なる部分については、その都度説明する。なお補助ヒータ６は必須の構成ではないため、図９では記載を省略しているが、実施例１及び実施例２と同様に補助ヒータ６を設けてもよい。本実施例のセンサ素子５０について、以下説明する。 In this embodiment, the compressibility of the region B in which the detection heater 5 is formed is enhanced as compared with other regions A by forming the oxide film serving as a compressible insulating film into a pressure film. The same configurations as those of the first to fourth embodiments are denoted by the same reference numerals as those of the first to fourth embodiments, and the description thereof is omitted. Moreover, about the structure which attached | subjected the same code | symbol, a different part from another Example is demonstrated each time. Since the auxiliary heater 6 is not an essential configuration, the description is omitted in FIG. 9, but the auxiliary heater 6 may be provided in the same manner as in the first and second embodiments. The sensor element 50 of the present embodiment will be described below.
　本実施例では、単結晶シリコンから成る基板２の表面に圧縮性絶縁膜５１ａを形成する。圧縮性絶縁膜５１ａとしては、主に酸化シリコンからなり熱酸化膜やＣＶＤ（Chemical Vapor Deposition）によって形成することができる。 In this embodiment, a compressible insulating film 51a is formed on the surface of the substrate 2 made of single crystal silicon. The compressible insulating film 51a is mainly made of silicon oxide and can be formed by a thermal oxide film or CVD (Chemical Vapor Deposition).
　圧縮性絶縁膜５１ａ上には、引張性絶縁膜５２ａが形成される。引張性絶縁膜５２ａとしては、例えばＣＶＤ法により形成した窒化シリコン膜を用いることができる。引張性絶縁膜５２ａは空洞部３上を完全に覆うように均一な膜厚で形成している。 A tensile insulating film 52a is formed on the compressible insulating film 51a. As the tensile insulating film 52a, for example, a silicon nitride film formed by a CVD method can be used. The tensile insulating film 52a is formed with a uniform film thickness so as to completely cover the cavity 3.
　引張性絶縁膜５２ａ上には同様な手法で酸化シリコンからなる圧縮性絶縁膜５１ｂを形成する。 A compressive insulating film 51b made of silicon oxide is formed on the tensile insulating film 52a in the same manner.
　次に、金属膜をスパッタ法などにより形成し、パターニングすることにより検出ヒータ５及び補助ヒータ６を形成する。次に検出ヒータ５及び補助ヒータ６を保護するために、プラズマＣＶＤ法などを用いて酸化シリコンからなる圧縮性絶縁膜５１ｃを形成する。圧縮性絶縁膜５１ｃは検出ヒータ５が形成された領域を残して除去される。 Next, a detection heater 5 and an auxiliary heater 6 are formed by forming a metal film by sputtering or the like and patterning it. Next, in order to protect the detection heater 5 and the auxiliary heater 6, a compressive insulating film 51c made of silicon oxide is formed using a plasma CVD method or the like. The compressible insulating film 51c is removed leaving the region where the detection heater 5 is formed.
　次に引張性絶縁膜５２ｂを形成する。引張性絶縁膜５２ｂとしては、プラズマＣＶＤ法により形成した窒化シリコンを用いることができる。 Next, a tensile insulating film 52b is formed. As the tensile insulating film 52b, silicon nitride formed by a plasma CVD method can be used.
　最後に、酸化シリコンからなる圧縮性絶縁膜５１ｄを同様な手法で形成する。 Finally, a compressive insulating film 51d made of silicon oxide is formed by the same method.
　本実施例では、検出ヒータ５が形成された領域Ｂの圧縮性絶縁膜（酸化シリコン）を他の領域に比べ厚く形成した構成である。つまり、絶縁膜で形成された薄膜部４の合成応力が他の領域Ａに比べて部分的に圧縮性となる圧縮性領域Ｂが設けられ、この圧縮性領域Ｂに検出ヒータ５を配置している。これにより、検出ヒータ５が形成された領域Ｂを他の領域Ａに比べて圧縮性とし、他の領域Ａは引張性を強くすることが可能である。 In this embodiment, the compressive insulating film (silicon oxide) in the region B where the detection heater 5 is formed is thicker than other regions. That is, a compressive region B in which the combined stress of the thin film portion 4 formed of an insulating film is partially compressible compared to other regions A is provided, and the detection heater 5 is disposed in the compressive region B. Yes. As a result, the region B where the detection heater 5 is formed can be made more compressible than the other regions A, and the other regions A can be made more tensile.
　本実施例の構成では、圧縮性絶縁膜が厚く形成された領域Ａと圧縮性絶縁膜が薄く形成された領域Ｂとで、薄膜部４を形成する絶縁膜全体の厚みが異なる。そのため、薄膜部４の表面に突部（厚膜部）５３が形成される。突部（厚膜部）５３の段差部５３ａには前述したような外力による応力集中が発生しやすい。そのため、段差部５３ａを高さが緩やかに変化する段差となるように形成し、応力集中を緩和することが望ましい。具体的には、既知の手法であるＳＯＧ（Spin on Glass）、エッチバック、ＣＭＰ等により段差部を緩和し緩やかに膜厚が変化させることができる。 In the configuration of this example, the thickness of the entire insulating film forming the thin film portion 4 is different between the region A where the compressive insulating film is formed thick and the region B where the compressive insulating film is formed thin. Therefore, a protrusion (thick film portion) 53 is formed on the surface of the thin film portion 4. The step 53a of the protrusion (thick film portion) 53 is likely to cause stress concentration due to external force as described above. Therefore, it is desirable to reduce the stress concentration by forming the stepped portion 53a so as to have a step whose height changes gently. Specifically, the stepped portion can be relaxed and the film thickness can be changed gently by known methods such as SOG (Spinson Glass), etch back, and CMP.
　本実施例では、検出ヒータ５の上層（領域Ｂ）の圧縮性絶縁膜５１ｃを残して他の領域Ａの圧縮性絶縁膜５１ｃを取り除いた構成について説明したが、検出ヒータ５の下層の圧縮性絶縁膜５１ｂを用いて同様な構成とすることも可能である。つまり検出ヒータ５が形成された領域Ｂにおいて、他の領域Ａよりも圧縮性絶縁膜５１ｂが厚く形成されていれば、本発明の効果が得られる。 In the present embodiment, the configuration in which the compressive insulating film 51c in the other region A is removed while leaving the compressible insulating film 51c in the upper layer (region B) of the detection heater 5 has been described. A similar structure can be formed using the insulating film 51b. That is, if the compressive insulating film 51b is formed thicker than the other regions A in the region B where the detection heater 5 is formed, the effect of the present invention can be obtained.
　また本実施例で説明した構成において、領域Ａにおいて圧縮性絶縁膜５１ｃ又は圧縮性絶縁膜５１ｂを完全に除去するのではなく、領域Ｂにおける圧縮性絶縁膜５１ｃ又は圧縮性絶縁膜５１ｂの膜厚に対して領域Ａにおける圧縮性絶縁膜５１ｃ又は圧縮性絶縁膜５１ｂの膜厚を薄くする構成でも、本発明の効果が得られる可能性がある。 In the structure described in this embodiment, the compressive insulating film 51c or the compressive insulating film 51b is not completely removed in the region A, but the film thickness of the compressible insulating film 51c or the compressive insulating film 51b in the region B. On the other hand, even if the compressive insulating film 51c or the compressive insulating film 51b in the region A is thinned, the effect of the present invention may be obtained.
　上述した各実施例により、以下の熱式センサ装置が得られる。
（１）基板２に形成した空洞部３を絶縁膜１１ａ～１１ｄ，１２ａ～１２ｃ，２１ａ～２１ｅ，２２ａ～２２ｃ，５１ａ～５１ｄ，５２ａ，５２ｂで覆った薄膜部４と、薄膜部４に形成した発熱体５と、を備えた熱式センサ装置において、薄膜部４における前記絶縁膜に部分的に圧縮性を強めた圧縮性領域Ｂが設けられ、圧縮性領域Ｂに発熱体５が配置される。
（２）（１）において、圧縮性領域Ｂの周辺の前記絶縁膜に引張性領域Ａが形成される。
（３）（２）において、前記絶縁膜の空洞部３の上を覆う部分は、室温において基板２に対して圧縮性となる圧縮応力膜１１ａ～１１ｄ，２１ａ～２１ｅ，５１ａ～５１ｄと、基板２に対して引張性となる引張応力膜１２ａ～１２ｃ，２２ａ～２２ｃ，５２ａ，５２ｂとからなり、圧縮性領域Ｂにおいて前記引張応力膜が部分的に除去されている。
（４）（３）において、前記絶縁膜の前記部分は、発熱体５の下層側に形成された下層側引張応力膜２２ａと、発熱体５の上層側に形成された上層側引張応力膜２２ｃと、下層側引張応力膜２２ａと上層側引張応力膜２２ｃとの間に形成された中間引張応力膜２２ｂと、を備え、圧縮性領域Ｂにおいて中間引張応力膜２２ｂが部分的に除去されている。
（５）（４）において、中間引張応力膜２２ｂは、上層引張応力膜２２ｃ及び下層側引張応力膜２２ａよりも厚く形成される。
（６）（３）において、前記絶縁膜の前記部分は、引張応力膜２２ｂがスリット状に除去された領域Ｃを備える。
（７）（３）において、引張応力膜１２ａは、圧縮性領域Ｂにおいて、多角形または円形に除去されている。
（８）（３）において、圧縮応力膜１１ａ～１１ｄ，２１ａ～２１ｅ，５１ａ～５１ｄは酸化シリコンを主とする絶縁膜であり引張応力膜は窒化シリコン１２ａ～１２ｃ，２２ａ～２２ｃ，５２ａ，５２ｂを主とする絶縁膜である。
（９）（３）において、発熱体５は金属材料である。 According to each of the embodiments described above, the following thermal sensor device is obtained.
(1) The hollow portion 3 formed in the substrate 2 is formed in the thin film portion 4 covered with the insulating films 11a to 11d, 12a to 12c, 21a to 21e, 22a to 22c, 51a to 51d, 52a and 52b, and the thin film portion 4. In the thermal sensor device including the heating element 5, the insulating film in the thin film portion 4 is provided with a compressible region B having a partially enhanced compressibility, and the heating element 5 is disposed in the compressive region B. The
(2) In (1), a tensile region A is formed in the insulating film around the compressive region B.
(3) In (2), the portions of the insulating film covering the cavity 3 are compressed stress films 11a to 11d, 21a to 21e, and 51a to 51d that are compressible with respect to the substrate 2 at room temperature, and the substrate. 2, tensile stress films 12a to 12c, 22a to 22c, 52a, and 52b that are tensile with respect to 2 are partially removed in the compressive region B.
(4) In (3), the insulating film includes the lower layer side tensile stress film 22a formed on the lower layer side of the heating element 5 and the upper layer side tensile stress film 22c formed on the upper layer side of the heating element 5. And an intermediate tensile stress film 22b formed between the lower tensile stress film 22a and the upper tensile stress film 22c, and the intermediate tensile stress film 22b is partially removed in the compressive region B. .
(5) In (4), the intermediate tensile stress film 22b is formed thicker than the upper tensile stress film 22c and the lower tensile stress film 22a.
(6) In (3), the portion of the insulating film includes a region C in which the tensile stress film 22b is removed in a slit shape.
(7) In (3), the tensile stress film 12a is removed in the compressive region B into a polygon or a circle.
(8) In (3), the compressive stress films 11a to 11d, 21a to 21e, 51a to 51d are insulating films mainly composed of silicon oxide, and the tensile stress films are silicon nitrides 12a to 12c, 22a to 22c, 52a, 52b. It is an insulating film mainly composed of
(9) In (3), the heating element 5 is a metal material.
　なお、本発明は上記した各実施例に限定されるものではなく、様々な変形例が含まれる。例えば、上記した実施例は本発明を分かりやすく説明するために詳細に説明したものであり、必ずしも全ての構成を備えるものに限定されるものではない。また、ある実施例の構成の一部を他の実施例の構成に置き換えることが可能であり、また、ある実施例の構成に他の実施例の構成を加えることも可能である。また、各実施例の構成の一部について、他の構成の追加・削除・置換をすることが可能である。 In addition, this invention is not limited to each above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
　１，２０，３０，４０，５０…センサ素子、２…基板、３・・・空洞部、４・・・薄膜部、５・・・検出ヒータ、６・・・補助ヒータ、７ａ～７ｄ・・・電極パッド、８ａ～８ｃ・・・抵抗、９ａ・・・差動増幅器、１０ａ～１０ｃ・・・抵抗、１１ａ～１１ｄ，２１ａ～２１ｅ，５１ａ～５１ｄ・・・圧縮性絶縁膜、１２ａ～１２ｃ，２２ａ～２２ｃ，５２ａ，５２ｂ・・・引張性絶縁膜、１００…熱式センサ装置、Ａ…引張性領域、Ｂ…圧縮性領域。 1, 20, 30, 40, 50 ... sensor element, 2 ... substrate, 3 ... cavity, 4 ... thin film part, 5 ... detection heater, 6 ... auxiliary heater, 7a-7d ... Electrode pads, 8a to 8c ... resistor, 9a ... differential amplifier, 10a to 10c ... resistor, 11a to 11d, 21a to 21e, 51a to 51d ... compressible insulating film, 12a to 12c , 22a to 22c, 52a, 52b ... tensile insulating film, 100 ... thermal sensor device, A ... tensile region, B ... compressive region.

Claims (9)

  1. 　基板に形成した空洞部を絶縁膜で覆った薄膜部と、前記薄膜部に形成した発熱体と、を備えた熱式センサ装置において、
    　前記薄膜部における前記絶縁膜に部分的に圧縮性を強めた圧縮性領域が設けられ、前記圧縮性領域に前記発熱体を配置したことを特徴とする熱式センサ装置。     In a thermal sensor device comprising a thin film portion in which a cavity formed in a substrate is covered with an insulating film, and a heating element formed in the thin film portion,
    A thermal sensor device, wherein the insulating film in the thin film portion is provided with a compressible region having a partially enhanced compressibility, and the heating element is disposed in the compressive region.
  2. 　請求項１に記載の熱式センサ装置において、
    　前記圧縮性領域の周辺の前記絶縁膜に引張性領域が形成されることを特徴とする熱式センサ装置。     The thermal sensor device according to claim 1,
    A thermal sensor device, wherein a tensile region is formed in the insulating film around the compressive region.
  3. 　請求項２に記載の熱式センサ装置において、
    　前記絶縁膜の前記空洞部の上を覆う部分は、室温において前記基板に対して圧縮性となる圧縮応力膜と、前記基板に対して引張性となる引張応力膜とからなり、前記圧縮性領域において前記引張応力膜が部分的に除去されていることを特徴とする熱式センサ装置。     The thermal sensor device according to claim 2,
    The portion of the insulating film that covers the cavity is composed of a compressive stress film that is compressive to the substrate at room temperature and a tensile stress film that is tensile to the substrate, and the compressive region. A thermal sensor device in which the tensile stress film is partially removed.
  4. 　請求項３に記載の熱式センサ装置において、
    　前記絶縁膜の前記部分は、前記発熱体の下層側に形成された下層側引張応力膜と、前記発熱体の上層側に形成された上層側引張応力膜と、前記下層側引張応力膜と前記上層側引張応力膜との間に形成された中間引張応力膜と、を備え、前記圧縮性領域において前記中間引張応力膜が部分的に除去されていることを特徴とする熱式センサ装置。     The thermal sensor device according to claim 3,
    The portion of the insulating film includes a lower tensile stress film formed on a lower layer side of the heating element, an upper tensile stress film formed on an upper layer side of the heating element, the lower tensile stress film, and the And an intermediate tensile stress film formed between the upper tensile stress film and the intermediate tensile stress film is partially removed in the compressive region.
  5. 　請求項４に記載の熱式センサ装置において、
    　前記中間引張応力膜は、前記上層側引張応力膜及び前記下層側引張応力膜よりも厚く形成されることを特徴とする熱式センサ装置。     The thermal sensor device according to claim 4,
    The thermal sensor device, wherein the intermediate tensile stress film is formed thicker than the upper tensile stress film and the lower tensile stress film.
  6. 　請求項３に記載の熱式センサ装置において、
    　前記絶縁膜の前記部分は、前記引張応力膜がスリット状に除去された領域を備えることを特徴とする熱式センサ装置。     The thermal sensor device according to claim 3,
    The thermal sensor device according to claim 1, wherein the portion of the insulating film includes a region where the tensile stress film is removed in a slit shape.
  7. 　請求項３に記載の熱式センサ装置において、
    　前記引張応力膜は、前記圧縮性領域において、多角形または円形に除去されていることを特徴とする熱式センサ装置。     The thermal sensor device according to claim 3,
    The thermal stress sensor is characterized in that the tensile stress film is removed in a polygonal or circular shape in the compressive region.
  8. 　請求項３に記載の熱式センサ装置において、
    　前記圧縮応力膜は酸化シリコンを主とする絶縁膜であり、前記引張応力膜は窒化シリコンを主とする絶縁膜であることを特徴とする熱式センサ装置。     The thermal sensor device according to claim 3,
    The thermal sensor device, wherein the compressive stress film is an insulating film mainly made of silicon oxide, and the tensile stress film is an insulating film mainly made of silicon nitride.
  9. 　請求項３に記載の熱式センサ装置において、
    　前記発熱体は金属材料であることを特徴とする熱式センサ装置。     The thermal sensor device according to claim 3,
    The thermal sensor device, wherein the heating element is a metal material.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000002571A (en) * 1998-06-16 2000-01-07 Tokyo Gas Co Ltd Hot wire type microheater
US20070231942A1 (en) * 2001-01-10 2007-10-04 Vanha Ralph S Micromechanical flow sensor with tensile coating
EP2348292A1 (en) * 2010-01-13 2011-07-27 Sensirion AG Sensor device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000002571A (en) * 1998-06-16 2000-01-07 Tokyo Gas Co Ltd Hot wire type microheater
US20070231942A1 (en) * 2001-01-10 2007-10-04 Vanha Ralph S Micromechanical flow sensor with tensile coating
EP2348292A1 (en) * 2010-01-13 2011-07-27 Sensirion AG Sensor device

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