WO2023188760A1 - Detection device and production method for same - Google Patents

Abstract

According to the present invention, a detection device comprises: a substrate 10; a first piezoelectric thin film resonator 11a that comprises a first lower electrode 12a that is provided on the substrate, a first piezoelectric layer 14a that is provided on the first lower electrode, a first upper electrode 16a that is provided on the first piezoelectric layer, a first resonance region 50a at which the first lower electrode and the first upper electrode are opposite with at least a portion of the first piezoelectric layer therebetween, and a sensing film that is provided on the first upper electrode in the first resonance region; a second piezoelectric thin film resonator 11b that comprises a second lower electrode 12b that is provided on the substrate, a second piezoelectric layer 14b that is provided on the second lower electrode, a second upper electrode 16b that is provided on the second piezoelectric layer, and a second resonance region 50b at which the second lower electrode and the second upper electrode are opposite with at least a portion of the second piezoelectric layer therebetween; and a heater 31 that is provided on the substrate and controlled on the basis of the resonant frequency of the second piezoelectric thin film resonator.

Description

Detection device and its manufacturing method

The present invention relates to a detection device and a method for manufacturing the same, and for example, to a detection device having a piezoelectric thin film resonator and a method for manufacturing the same.

A detection device is known in which a sensitive film is provided on the upper electrode of a piezoelectric thin film resonator and detects changes in the environment based on changes in the resonant frequency or anti-resonant frequency due to changes in the mass of the sensitive film (for example, Patent Documents 1 and 2). ). Detection devices having a detection element that detects changes in the environment and a temperature element that detects temperature are known (for example, Patent Documents 3 to 8).

Japanese Patent Application Publication No. 2018-115927 Japanese Patent Application Publication No. 2015-139167 JP2020-139788A Japanese Patent Application Publication No. 2004-294356 Japanese Patent Application Publication No. 7-300512 Japanese Patent Application Publication No. 2004-37224 JP2018-48930A Japanese Patent Application Publication No. 2021-196354

When using a heater and a temperature element to control the temperature of a detection element, it is required to control the temperature with high precision.

The present invention was made in view of the above-mentioned problems, and an object thereof is to control temperature with high precision.

The present invention includes a substrate, a first lower electrode provided on the substrate, a first piezoelectric layer provided on the first lower electrode, and a first upper electrode provided on the first piezoelectric layer. a first resonant region in which the first lower electrode and the first upper electrode face each other with at least a portion of the first piezoelectric layer in between; and a first resonant region provided on the first upper electrode in the first resonant region. a first piezoelectric thin film resonator comprising: a second piezoelectric thin film resonator comprising: a second lower electrode provided on the substrate; a second piezoelectric layer provided on the second lower electrode; a second piezoelectric thin film resonator comprising: a second upper electrode provided in the second piezoelectric layer; and a second resonance region in which the second lower electrode and the second upper electrode face each other with at least a portion of the second piezoelectric layer sandwiched therebetween. and a heater provided on the substrate and controlled based on the resonance frequency of the second piezoelectric thin film resonator.

In the above configuration, the heater may be provided adjacently between the first piezoelectric thin film resonator and the second piezoelectric thin film resonator.

In the above configuration, the first resonant region is connected to the heater in a direction intersecting a direction in which the first lower electrode is drawn out from the first resonant region and a direction in which the first upper electrode is drawn out from the first resonant region. , the second resonance region is adjacent to the heater in a direction intersecting a direction in which the second lower electrode is drawn out from the second resonance region and a direction in which the second upper electrode is drawn out from the second resonance region. It can be configured so that it is adjacent to the .

In the above configuration, a first gap is provided under the first lower electrode in the first resonance region, a second gap is provided below the second lower electrode in the second resonance region, and a second gap is provided under the second lower electrode in the first resonance region. A first portion of the electrode, excluding a portion provided on the first substrate outside the first gap and connecting the first lower electrode to the outside, is located closest to the heater of the first piezoelectric thin film resonator. , and a second portion of the second lower electrode other than a portion provided on the second substrate outside the second gap and connecting the second lower electrode with the outside is a second portion of the second piezoelectric thin film resonance. Among the devices, the configuration may be the one closest to the heater.

In the above configuration, the shortest distance between the first portion and the heater may be 0.5 times or more and twice or less the shortest distance between the second portion and the heater.

In the above configuration, a third piezoelectric layer is provided on the substrate between the first piezoelectric thin film resonator and the second piezoelectric thin film resonator, and is continuous with the first piezoelectric layer and the second piezoelectric layer. The heater may be provided between the substrate and the third piezoelectric layer.

In the above configuration, the heater is connected to the first lower electrode in a region where the first lower electrode is drawn out from the first resonance region, and the second lower electrode is drawn out from the second resonance region. The structure may be such that it is joined to the second lower electrode in the region.

In the above configuration, the heater is arranged such that the first upper electrode is connected to the first piezoelectric layer in a first region drawn out from the first resonant region or in a region opposite to the first resonant region with respect to the first region. and the second upper electrode is bonded to the second piezoelectric layer in a second region drawn out from the second resonant region or in a region opposite to the second resonant region with respect to the second region. be able to.

In the above configuration, a first gap is provided under the first lower electrode in the first resonance region, a second gap is provided below the second lower electrode in the second resonance region, and the heater is , may be provided within the first gap and the second gap.

In the above configuration, the first lower electrode and the second lower electrode are made of substantially the same material and have substantially the same thickness, and the first piezoelectric layer and the second piezoelectric layer are substantially The first upper electrode and the second upper electrode may be made of substantially the same material and have substantially the same thickness. can.

In the above configuration, the shortest distance between the first resonance region and the heater is at least 0.5 times and at most twice the shortest distance between the second resonance region and the heater. be able to.

In the above configuration, the first piezoelectric thin film resonator includes a temperature compensation film between the first lower electrode and the first upper electrode in at least a central portion of the first resonance region, and the second piezoelectric thin film resonator The device may be configured such that a temperature compensation film is not provided between the second lower electrode and the second upper electrode in a central portion of the second resonance region.

In the above configuration, the heater may be a conductor line provided on the substrate.

The above configuration may include a detector that detects a change in the environment based on the resonant frequency of the first piezoelectric thin film resonator and controls the heater based on the resonant frequency of the second piezoelectric thin film resonator. I can do it.

The present invention includes a step of forming a first lower electrode and a second lower electrode from the same metal layer on a substrate, and forming a first piezoelectric layer and a second piezoelectric layer on the first lower electrode and the second lower electrode, respectively. a first piezoelectric thin film resonator having a step of forming the same piezoelectric layer, and a first resonance region in which the first lower electrode and the first upper electrode face each other with at least a portion of the first piezoelectric layer sandwiched therebetween; the first piezoelectric layer and a second piezoelectric thin film resonator having a second resonance region in which the second lower electrode and the second upper electrode face each other with at least a portion of the two piezoelectric layers sandwiched therebetween. forming the first upper electrode and the second upper electrode from the same metal layer on the second piezoelectric layer; and forming a sensitive film on the first upper electrode in the first resonance region. . A method of manufacturing a detection device, comprising: forming on the substrate a heater that is controlled based on the resonance frequency of the second piezoelectric thin film resonator.

In the above configuration, the step of forming a temperature compensation film between the first lower electrode and the first upper electrode and between the second lower electrode and the second upper electrode; The method may include a step of leaving the temperature compensation film in at least a central portion and removing the temperature compensation film in at least a central portion of the second resonance region.

According to the present invention, temperature can be controlled with high accuracy.

FIG. 1 is a block diagram of a detection device according to a first embodiment. FIG. 2 is a plan view of the sensor according to the first embodiment. 3(a) and 3(b) are a sectional view taken along the line AA and sectional view taken along the line BB in FIG. 2, respectively. FIGS. 4(a) to 4(d) are cross-sectional views showing a method of manufacturing a sensor in Example 1. FIG. 5(a) to 5(c) are cross-sectional views showing a method for manufacturing a sensor in Example 1. FIG. 6(a) to 6(c) are cross-sectional views showing a method for manufacturing a sensor in Example 1. FIG. FIGS. 7(a) to 7(d) are cross-sectional views showing a method of forming an inserted film in Example 1. FIG. 8 is a diagram showing the amount of change Δf in the resonance frequency of the piezoelectric thin film resonator with respect to time in Experiment 1. FIG. 9(a) is a diagram showing the resonant frequency of the piezoelectric thin film resonator with respect to time in Experiment 2, and FIG. 9(b) is a diagram showing the temperature with respect to the current of the heating line in the simulation. FIG. 10 is a plan view of a sensor in Example 2. FIGS. 11(a) and 11(b) are a sectional view taken along line AA and taken along line BB in FIG. 10, respectively. FIG. 12 is a plan view of a sensor in Modification 1 of Embodiment 2. 13(a) and 13(b) are a sectional view taken along line AA and taken along line BB in FIG. 12, respectively. FIG. 14 is a sectional view taken along the line CC in FIG. 12. FIG. 15 is a cross-sectional view of a sensor in Example 3. FIG. 16 is a cross section taken along the line AA in FIG. 15. FIG. 17 is a plan view of a sensor in Example 4. 18(a) is a cross-sectional view taken along the line AA in FIG. 17, and FIG. 18(b) is a cross-sectional view of the sensor in Modification 1 of Example 4. FIG. 19 is a plan view of a sensor in Example 5. FIG. 20 is a plan view of a sensor in Example 6. FIG. 21 is a sectional view taken along line AA in FIG. 20. 22(a) and 22(b) are cross-sectional views of the sensor in Example 7 and Modification Example 1, respectively.

Examples will be described below with reference to the drawings.

FIG. 1 is a block diagram of a detection device according to the first embodiment. As shown in FIG. 1, the detection device 100 includes a sensor 40 and a detector 42. In the sensor 40, piezoelectric thin film resonators 11a, 11b and a heater 31 are provided on a substrate 10. The piezoelectric thin film resonator 11a is a detection element that detects changes in the environment, and the piezoelectric thin film resonator 11b is a temperature element that detects the temperature of the substrate 10. The heater 31 heats the substrate 10.

The detector 42 includes oscillation circuits 44a, 44b, measuring devices 45a, 45b, a control section 46, and a calculation section 47. Oscillation circuits 44a and 44b output oscillation signals having oscillation frequencies corresponding to the resonance frequencies of piezoelectric thin film resonators 11a and 11b, respectively. Note that the oscillation circuits 44a and 44b can also be said to include piezoelectric thin film resonators 11a and 11b, respectively, and constitute an oscillation circuit. The oscillation frequency does not need to be the same as the resonant frequency, and it is sufficient that the oscillation frequency changes based on a change in the resonant frequency. Measuring devices 45a and 45b measure the frequencies of oscillation signals output by oscillation circuits 44a and 44b, respectively. The calculation unit 47 calculates the change in the environment based on the amount of change in the frequency of the oscillation signal measured by the measuring device 45a. The control unit 46 detects the temperature based on the amount of change in the frequency of the oscillation signal measured by the measuring device 45b. The control unit 46 controls the heater 31 based on the detected temperature. In this way, the detector 42 detects changes in the environment based on the resonance frequency of the piezoelectric thin film resonator 11a (first piezoelectric thin film resonator), and detects the resonance of the piezoelectric thin film resonator 11b (second piezoelectric thin film resonator). The heater 31 is controlled based on the frequency.

For example, the control unit 46 controls the heater 31 based on the detected temperature, and sets the temperature of the piezoelectric thin film resonator 11a to a desired temperature. Thereafter, the control unit 46 causes the calculation unit 47 to detect a change in the environment based on a change in the resonance frequency of the piezoelectric thin film resonator 11a. Note that a change in the environment refers to a change in the concentration of a specific substance such as a specific atom or molecule in a gas or liquid, a change in humidity, etc., and includes, for example, detecting a specific substance in the gas or liquid.

Next, the sensor 40 of Example 1 will be explained. FIG. 2 is a plan view of the sensor 40 according to the first embodiment. 3(a) and 3(b) are a sectional view taken along the line AA and sectional view taken along the line BB in FIG. 2, respectively. In FIG. 2, the resonance regions 50a, 50b and the heat generating line 30 are shown by cross hatching, the upper electrodes 16a, 16b, the pads 24a, 24b, 24d, 25a, 25b and 25d are shown by solid lines, the lower electrodes 12a, 12b, the sensitive film 18, The voids 22a and 22b are indicated by broken lines. The normal direction of the upper surface of the substrate 10 is the Z direction, the arrangement direction of the piezoelectric thin film resonators 11a and 11b is the X direction, and the direction perpendicular to the X direction among the plane directions is the Y direction.

As shown in FIGS. 2 to 3(b), piezoelectric thin film resonators 11a and 11b are provided on a substrate 10 having a rectangular planar shape. A heating line 30 is provided as a heater 31 between the piezoelectric thin film resonators 11a and 11b. The heating line 30 has a structure in which a pair of electrodes such as the pads 24d and 24d are connected by a metal line, a voltage is applied to the pair of electrodes, and Joule heat is generated by a current flowing through the metal line.

In the piezoelectric thin film resonator 11a, a lower electrode 12a (first lower electrode) is provided on the substrate 10, a piezoelectric layer 14a (first piezoelectric layer) is provided on the lower electrode 12a, and an upper electrode 16a is provided on the piezoelectric layer 14a. (first upper electrode) is provided. A gap 22a (first gap) having a dome-shaped bulge is formed between the flat upper surface of the substrate 10 and the lower electrode 12a. The dome-shaped bulge is a bulge having a shape such that, for example, the height of the void 22a is small around the void 22a, and the height of the void 22a becomes larger toward the inside of the void 22a. The resonance region 50a (first resonance region) is defined by a region where the lower electrode 12a and the upper electrode 16a face each other with at least a portion of the piezoelectric layer 14a in between. The resonance region 50a has an elliptical shape, and is a region where elastic waves such as a thickness longitudinal vibration mode or a thickness shear vibration mode resonate. The planar shape of the resonance region 50a may be other than an elliptical shape, and may be, for example, a polygonal shape such as a quadrangular shape or a pentagonal shape.

In plan view, the air gap 22a is provided with the same size as the resonance region 50a or larger than the resonance region 50a. Thereby, the elastic wave is reflected by the air gap 22a. The lower electrode 12a is provided larger than the gap 22a, and the peripheral edge of the lower electrode 12a is provided on the substrate 10 outside the gap 22a. Holes 23a are provided in the lower electrode 12a located on both sides of the resonance region 50a in the X direction. The hole 23a is connected to the void 22a. As will be described later, the hole 23a is a hole through which an etching solution for etching the sacrificial layer passes when forming the void 22a.

A sensitive film 18 is provided on the upper electrode 16a. A recess 19 corresponding to the insertion film 20a is provided on the upper surface of the upper electrode 16a, and the sensitive film 18 is provided within the recess 19. Thereby, when forming the sensitive film 18, the area where the sensitive film 18 is provided can be made constant.

For example, when a substance such as a specific atom or molecule in a gas or liquid is adsorbed to the sensitive film 18, the mass of the sensitive film 18 increases. When the humidity around the sensitive film 18 increases, moisture is adsorbed to the sensitive film 18 and the mass of the sensitive film 18 increases. When the temperature changes, the mass of the sensitive film 18 changes. When the sensitive film 18 is irradiated with light such as ultraviolet rays, the mass of the sensitive film 18 changes. In this way, the mass of the sensitive film 18 changes due to changes in the environment such as the concentration of a specific substance in the gas or liquid surrounding the sensitive film 18, humidity, temperature, or light intensity. When the mass of the sensitive film 18 changes, the resonant frequency of the piezoelectric thin film resonator 11a changes. In this way, the piezoelectric thin film resonator 11a can be used as a detection element for detecting changes in the environment.

The piezoelectric layer 14 includes a lower piezoelectric layer 15a provided on the substrate 10 and an upper piezoelectric layer 15b provided on the lower piezoelectric layer 15a. An insertion film 20a is provided between the lower piezoelectric layer 15a and the upper piezoelectric layer 15b over the entire surface of the resonant region 50a. The insertion film 20a at the periphery of the resonance region 50a is thicker than the insertion film 20a at the center. The insertion film 20a at the center of the resonance region 50a functions as a temperature compensation film for reducing the temperature coefficient, and the insertion film 20a at the peripheral portion functions as a film for improving the Q value. When the Q value is not improved, the thickness of the insertion film 20a at the peripheral portion may be the same as the thickness of the insertion film 20a at the center. In the piezoelectric thin film resonator 11a, the temperature coefficient of the resonance frequency is reduced by providing the insertion film 20a that functions as a temperature compensation film. The insertion film 20a may be provided between the lower electrode 12a and the upper electrode 16a. For example, the insertion film 20a may be provided between the lower electrode 12a and the piezoelectric layer 14, or may be provided between the piezoelectric layer 14 and the upper electrode 16a. By providing the insertion film 20a between the upper piezoelectric layer 15b and the lower piezoelectric layer 15a, the insertion film 20a can exhibit a better temperature compensation effect.

The lower electrode 12a is drawn out from the resonance region 50a in the −Y direction. The region where the lower electrode 12a is drawn out from the resonance region 50a is a region 52a. In region 52a, piezoelectric layer 14 and upper electrode 16a are not provided on lower electrode 12a, but pad 24a is provided on lower electrode 12a. The upper electrode 16a is drawn out from the resonance region 50a in the +Y direction. The region where the upper electrode 16a is drawn out from the resonance region 50a is a region 54a. In region 54a, lower electrode 12a is not provided, piezoelectric layer 14 is provided on substrate 10, and upper electrode 16a is provided on piezoelectric layer 14. A pad 25a is provided on the upper electrode 16a.

The piezoelectric layer 14 other than the area where the upper electrode 16a is provided has been removed. Thereby, it is possible to suppress the elastic waves from propagating through the piezoelectric layer 14 from the resonance regions 50a and 50b and leaking to the outside. Therefore, loss reduction due to leakage of elastic wave energy can be suppressed, and the Q value can be improved.

The piezoelectric thin film resonator 11b includes a lower electrode 12b (second lower electrode) on the substrate 10, a piezoelectric layer 14b (second piezoelectric layer) on the lower electrode 12b, and an upper electrode 16b (second upper electrode) on the piezoelectric layer 14b. is provided similarly to the piezoelectric thin film resonator 11a. A gap 22b (second gap) is provided between the substrate 10 and the lower electrode 12b. Pads 24b and 25b are provided similarly to pads 24a and 25a in piezoelectric thin film resonator 11a. The resonance region 50b (second resonance region) is defined by a region where the lower electrode 12b and the upper electrode 16b face each other with at least a portion of the piezoelectric layer 14b interposed therebetween. The region 52b is a region where the lower electrode 12b is drawn out from the resonance region 50b, and the region 54b is a region where the upper electrode 16b is drawn out from the resonance region 50b.

In the piezoelectric thin film resonator 11b, the insertion film 20b is provided at the periphery of the resonant region 50b, and is not provided at the center of the resonant region 50b. The insertion film 20b functions as a film for improving the Q value, but does not function as a temperature compensation film. If the Q value is not to be improved, the insertion film 20b may not be provided. In the piezoelectric thin film resonator 11b, since a temperature compensation film is not provided, the resonant frequency changes depending on the temperature. Therefore, the piezoelectric thin film resonator 11b can be used as a temperature element.

A heating line 30 is provided on the substrate 10 between the piezoelectric thin film resonators 11a and 11b with an insulating layer 32 in between. The heat generating line 30 is, for example, a metal layer, and has a meandering planar shape. The insulating layer 32 is provided to insulate the heating line 30 and the substrate 10. If the insulation of the substrate 10 is high, the insulation layer 32 may not be provided. Both ends of the heating line 30 are electrically connected to pads 24d and 25d. The pads 24d and 25d are provided on both sides of the heat generating line 30 in the Y direction. When the control unit 46 applies a voltage between the pads 24d and 25d and causes a current to flow through the heat generating line 30, the heat generating line 30 generates heat.

In the piezoelectric thin film resonator 11a, the portion closest to the heating line 30 is a portion 13a of the lower electrode 12a provided on the side of the heating line 30 of the substrate 10 outside the gap 22a. Portion 13a is located near hole 23a. The shortest distance between the piezoelectric thin film resonator 11a and the heating line 30 in plan view is La. In the piezoelectric thin film resonator 11b, the portion closest to the heating line 30 is a portion 13b (near the hole 23b) of the lower electrode 12b provided on the side of the heating line 30 of the substrate 10 outside the gap 22b. The shortest distance between the piezoelectric thin film resonator 11b and the heating line 30 in plan view is Lb. Portion 13b is located near hole 23b. The distances La and Lb are approximately equal.

The substrate 10 is, for example, a silicon substrate, a sapphire substrate, a quartz substrate, a glass substrate, a ceramic substrate, or a GaAs substrate. The lower electrodes 12a, 12b and the upper electrodes 16a and 16b are made of, for example, ruthenium (Ru), chromium (Cr), aluminum (Al), titanium (Ti), copper (Cu), molybdenum (Mo), tungsten (W), tantalum. It is a single layer film of (Ta), platinum (Pt), rhodium (Rh), or iridium (Ir), or a laminated film selected from a plurality of these films.

The piezoelectric layer 14 is made of, for example, an aluminum nitride (AlN) film, a zinc oxide (ZnO) film, a gallium nitride (GaN) film, a lead zirconate titanate (PZT) film, a lead titanate (PbTiO ₃ ) film, a lithium tantalate ( LiTaO ₃ ) film or lithium niobate (LiNbO ₃ ) film.

The center portion of the resonant region 50a of the insertion film 20a has a temperature coefficient of elastic constant with a sign opposite to that of the piezoelectric layer 14. Thereby, temperature coefficients such as resonance frequency can be brought close to zero. The peripheral edges of the resonant regions 50a and 50b of the insertion films 20a and 20b include a film of a material having a smaller Young's modulus than the piezoelectric layer 14. As such a material, the insertion films 20a and 20b are, for example, a silicon oxide film.

The pads 24a, 24b, 24d, 25a, 25b, and 25d are, for example, a low resistance film such as a gold film, a copper film, or an aluminum film, and may have an adhesive film such as a titanium film. This is a gold film on a titanium film. Insulating layer 32 is, for example, a silicon oxide layer or a silicon nitride layer. The heating line 30 is a line-shaped metal layer that generates heat, and is made of platinum, for example, and is, for example, a chromium film and a platinum film on the chromium film.

The sensitive film 18 is, for example, an organic polymer film, an organic low molecular film, or an inorganic film. Examples of organic polymer materials include polystyrene, polymethyl methacrylate, 6-nylon, cellulose acetate, poly-9,9-dioctylefluorene, polyvinyl alcohol, polyvinylcarbazole, polyethylene oxide, polyvinyl chloride, poly-p- Homopolymers consisting of a single structure such as phenylene ether sulfone, poly-1-butene, polybutadiene, polyphenylmethylsilane, polycaprolactone, polybisphenoxyphosphazene, polypropylene, etc.; copolymers that are copolymers of two or more homopolymers; Blend polymers made by mixing these can be used.

For example, organic low-molecular materials include tris(8-quinolinolato)aluminum (Alq3), naphthyldiamine (α-NPD), BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), and CBP. (4,4'-N,N'-dicarbazole-biphenyl), copper phthalocyanine, fullerene, pentacene, anthracene, thiophene, Ir(ppy(2-phenylpyridinato)) ₃ , triazinethiol derivative, dioctylfluorene derivative, tetratetracontane, Parylene or the like can be used.

For example, inorganic materials include alumina, titania, vanadium pentoxide, tungsten oxide, lithium fluoride, magnesium fluoride, aluminum, gold, silver, tin, indium tin oxide (ITO), carbon nanotubes, sodium chloride, chloride Magnesium or the like can be used.

The sensitive membrane 18 is a metal-organic structure in which organic ligands and metal ions are bonded, and may be a porous body having pores. The sensitive membrane 18 may be made of metal phthalocyanine such as copper phthalocyanine (CuPc), or may contain an antibody to which an antigen binds.

When using the piezoelectric thin film resonators 11a and 11b having a resonance frequency of 2.4 GHz, the lower electrodes 12a and 12b are a chromium film with a thickness of 70 nm and a ruthenium film with a thickness of 166 nm from the substrate 10 side. The lower piezoelectric layer 15a is an aluminum nitride film with a thickness of 498 nm, and the upper piezoelectric layer 15b is an aluminum nitride film with a thickness of 498 nm. The thickness of the insertion film 20a at the center of the resonant region 50a is 73 nm. The upper electrodes 16a and 16b are a ruthenium film with a thickness of 166 nm and a chromium film with a thickness of 55 nm from the piezoelectric layers 14a and 14b side. The sensitive film 18 is, for example, a polymer resin with a thickness of 80 nm. Insulating layer 32 is a silicon oxide layer with a thickness of 200 nm. The heating line 30 is a chromium layer with a thickness of 10 nm and a platinum layer with a thickness of 300 μm from the insulating layer 32 side.

[Sensor manufacturing method]
4(a) to 6(c) are cross-sectional views showing a method of manufacturing the sensor 40 in Example 1. FIG. As shown in FIG. 4(a), an insulating layer 32 is formed on the upper surface of the substrate 10. The substrate 10 is, for example, a wafer. The insulating layer 32 is formed using, for example, a CVD (Chemical Vapor Deposition) method, a sputtering method, or a vacuum evaporation method. The insulating layer 32 is patterned into a desired shape using photolithography and etching.

As shown in FIG. 4(b), sacrificial layers 38a and 38b are formed on the substrate 10 to form voids. The sacrificial layers 38a and 38b are, for example, a magnesium oxide (MgO) film, a zinc oxide (ZnO) film, a germanium (Ge) film, a silicon oxide (SiO ₂ ) film, or a phosphosilicate glass (PSG) film. The thickness of the sacrificial layers 38a and 38b is, for example, 10 to 100 nm. The sacrificial layers 38a and 38b are formed using a sputtering method, a vacuum evaporation method, or a CVD method. Thereafter, the sacrificial layers 38a and 38b are patterned into a desired shape using photolithography and etching. The shapes of the sacrificial layers 38a and 38b correspond to the planar shapes of the voids 22a and 22b.

As shown in FIG. 4(c), lower electrodes 12a and 12b are formed on the sacrificial layers 38a and 38b and the substrate 10 using, for example, sputtering, vacuum evaporation, or CVD, and then formed using photolithography and etching. pattern into the desired shape. The lower electrodes 12a and 12b may be formed by a lift-off method. As shown in FIG. 4D, a lower piezoelectric layer 15a is formed on the lower electrodes 12a and 12b, the insulating layer 32, and the substrate 10 using, for example, a sputtering method, a vacuum evaporation method, or a CVD method.

As shown in FIG. 5(a), insert films 20a and 20b are formed on the lower piezoelectric layer 15a using, for example, sputtering, vacuum evaporation, or CVD, and shaped into a desired shape using photolithography and etching. pattern. The insertion films 20a and 20b may be formed by a lift-off method. By providing the insertion film 20a with a thick film portion and a thin film portion, a recess 19a is formed on the upper surface of the insertion film 20a.

As shown in FIG. 5(b), an upper piezoelectric layer 15b is formed on the lower piezoelectric layer 15a and the insertion films 20a and 20b using, for example, a sputtering method, a vacuum evaporation method, or a CVD method. Piezoelectric layer 14 is formed from lower piezoelectric layer 15a and upper piezoelectric layer 15b. A recess 19b corresponding to the recess 19a on the upper surface of the insertion film 20a is formed on the upper surface of the upper piezoelectric layer 15b.

As shown in FIG. 5(c), upper electrodes 16a and 16b are formed on the upper piezoelectric layer 15b using, for example, a sputtering method, a vacuum evaporation method, or a CVD method, and a desired shape is formed using, for example, a photolithography technique and a lift-off method. Pattern into a shape. Upper electrodes 16a and 16b may be formed by a lift-off method. A recess 19 is formed on the upper surface of the upper electrode 16a, corresponding to the recess 19a on the upper surface of the insertion film 20a and the recess 19b on the upper surface of the upper piezoelectric layer 15b.

As shown in FIG. 6(a), the piezoelectric layer 14 is patterned into a desired shape using, for example, photolithography and etching. As a result, a piezoelectric layer 14a sandwiched between the lower electrode 12a and the upper electrode 16a and a piezoelectric layer 14b sandwiched between the lower electrode 12b and the upper electrode 16b are formed.

As shown in FIG. 6(b), a heat generating line 30 is formed on the insulating layer 32 using, for example, a photolithography method, a vacuum evaporation method, and a lift-off method. Pads 24a, 24b and 24d, 25a, 25b and 25d (see FIGS. 2 and 3(b)) are formed using, for example, a photolithography method, a vacuum evaporation method, and a lift-off method.

As shown in FIG. 6(c), the etching solution is introduced into the sacrificial layers 38a and 38b below the lower electrodes 12a and 12b through the holes 23a and 23b. As a result, sacrificial layers 38a and 38b are removed. It is preferable that the etching solution used to etch the sacrificial layers 38a and 38b does not etch the materials constituting the piezoelectric thin film resonators 11a and 11b other than the sacrificial layers 38a and 38b. In particular, it is preferable that the etching solution does not etch the lower electrodes 12a, 12b and the substrate 10. The stress of the lower electrode 12a, the piezoelectric layer 14a, and the upper electrode 16a, and the stress of the lower electrode 12b, the piezoelectric layer 14b, and the upper electrode 16b are set to be compressive stress. As a result, when the sacrificial layers 38a and 38b are removed, the lower electrodes 12a and 12b bulge away from the substrate 10 to the opposite side of the substrate 10. As a result, gaps 22a and 22b having dome-shaped bulges are formed between the lower electrodes 12a and 12b and the substrate 10.

As shown in FIG. 3(a), a sensitive film 18 is formed in the recess 19 on the upper surface of the upper electrode 16a. The sensitive film 18 is formed, for example, by applying a solvent in which the material of the sensitive film 18 is dissolved, and then drying the solvent. Further, the sensitive film 18 may be formed into a desired pattern using a sputtering method or a vacuum evaporation method and a lift-off method. Thereafter, the sensor 40 in Example 1 is manufactured by cutting the wafer into individual pieces.

A method for forming the insertion films 20a and 20b in FIG. 5(a) will be explained. FIGS. 7(a) to 7(d) are cross-sectional views showing a method of forming an inserted film in Example 1. Note that, for ease of understanding, the type of hatching for the membranes 21a and 21b is different from the type of hatching for the inserted membranes 20a and 20b. As shown in FIG. 7A, after the step of FIG. 4D, a film 21a is formed on the entire surface of the lower piezoelectric layer 15a using, for example, a sputtering method. The thickness of the film 21a is the same as the thickness of the inserted film 20b at the peripheral edge of the resonance region 50b (see FIG. 3(a)). As shown in FIG. 7(b), the film 21a other than the periphery of the resonance region 50a and the periphery of the resonance region 50b is removed using a photolithography method and an etching method.

As shown in FIG. 7C, a film 21b is formed on the entire surface of the lower piezoelectric layer 15a and the film 21a using, for example, a sputtering method. The thickness of the film 21b is the same as the thickness of the inserted film 20a at the center of the resonance region 50a (see FIG. 3(a)). As shown in FIG. 7D, the film 21b other than the resonance region 50a is removed using photolithography and etching. As a result, the insertion film 20a is formed from the film 21b at the center of the resonance region 50a, and the insertion film 20a is formed from the films 21a and 21b at the peripheral portion of the resonance region 50a. The insertion film 20b is not formed at the center of the resonance region 50b, and the insertion film 20b is formed from the film 21a at the periphery of the resonance region 50b. Other methods may be used to form intercalated membranes 20a and 20b.

[Example of controlling the temperature of the sensitive film 18]
In Example 1, as an example of controlling the temperature of the piezoelectric thin film resonator 11a using the heating line 30 and the piezoelectric thin film resonator 11b, Example 1) Initialization of the sensitive film 18 before detecting a change in the environment, Example 2 ) Temperature control when detecting changes in the environment.

[Initialization of the sensitive membrane 18 before detecting a change in the environment]
Initialization of the sensitive film 18 involves heating the sensitive film 18 in order to remove moisture and specific substances adsorbed onto the sensitive film 18 from the sensitive film 18. The temperature at which water and specific substances are desorbed depends on the material of the sensitive film 18 and the like. For example, the inventors measured the temperature at which water is desorbed from the polymer resin used as the sensitive film 18 using a simultaneous differential thermal and thermogravimetric measurement method. As a result, it was found that water was desorbed from the sensitive film 18 at a temperature of 50° C. to 80° C. Depending on the material of the sensitive film 18, the sensitive film 18 may be oxidized and deteriorated at temperatures below 100°C. As described above, it is important to control the temperature of the sensitive film 18 within a certain range in order to remove moisture and specific substances from the sensitive film 18 without degrading the sensitive film 18. In order to initialize the sensitive film 18 before detecting changes in the environment, by setting the temperature of the sensitive film 18 to a desired temperature, changes in the environment can be repeatedly and stably detected.

[Temperature control of the sensitive membrane 18 when detecting environmental changes: Experiment 1]
Experiment 1 was conducted to investigate the importance of temperature changes in the sensitive film 18. The layers and materials of the piezoelectric thin film resonator 11a used in Experiment 1 are as follows. Substrate 10 is a silicon substrate. The lower electrode 12a is a chromium film with a thickness of 70 nm and a ruthenium film with a thickness of 166 nm from the substrate 10 side. The lower piezoelectric layer 15a is a 498 nm thick aluminum nitride film oriented in the (002) direction, and the upper piezoelectric layer 15b is a 498 nm thick aluminum nitride film. The thickness of the insertion film 20a at the center of the resonant region 50a is 73 nm. The upper electrode 16a is a ruthenium film with a thickness of 166 nm and a chromium film with a thickness of 55 nm from the piezoelectric layers 14a and 14b side. The sensitive film 18 is, for example, a polymer resin with a thickness of 80 nm. The resonant frequency of the piezoelectric thin film resonator 11a is approximately 2.4 GHz.

The piezoelectric thin film resonator 11a was placed inside the chamber, and the temperature inside the chamber was kept constant. The humidity in the chamber was set at 0% to 1.8% to reduce the influence of moisture adsorption. Dry air containing ethanol at a concentration of 90 ppm was introduced into the chamber, and changes in the resonant frequency of the piezoelectric thin film resonator 11a were examined.

FIG. 8 is a diagram showing the amount of change Δf of the resonant frequency with respect to time of the piezoelectric thin film resonator in Experiment 1. Before the time on the horizontal axis reached 0 seconds, the temperature inside the chamber was raised to remove water and ethanol from the sensitive film 18, and then the inside of the chamber was stabilized at a desired temperature. At time 0 seconds, introduction of dry air containing ethanol was started. At 1750 seconds, introduction of dry air containing ethanol was stopped, and introduction of dry air not containing ethanol was started. Period T is the period during which dry air containing ethanol is introduced into the chamber. The vertical axis indicates the amount of change Δf in the resonance frequency from the resonance frequency when time is 0 seconds. Experiments were conducted with the temperature in the chamber stabilized at 18°C, 26°C, 40°C, and 50°C.

As shown in FIG. 8, when the temperature is 18° C., the amount of change Δf in the resonance frequency decreases with time, and after 1000 seconds, Δf stabilizes at about -30 kHz. At a temperature of 26° C., Δf stabilizes at about −22 kHz after 500 seconds. At a temperature of 40° C., Δf stabilizes at about −11 kHz after 100 seconds, but gradually increases after 500 seconds. At a temperature of 50° C., Δf decreases to about −7 kHz after 0 seconds, but thereafter, Δf gradually increases. Thus, the magnitude of Δf depends on temperature. Further, the time it takes for Δf to stabilize depends on the temperature. In this manner, when detecting changes in the environment based on changes in the resonant frequency of the piezoelectric thin film resonator 11a, it is important to control the temperature of the piezoelectric thin film resonator 11a.

[Experiment 2: Temperature dependence of resonance frequency of piezoelectric thin film resonator 11b]
Next, Experiment 2 was conducted to investigate whether the resonant frequency of the piezoelectric thin film resonator 11b changes with temperature. The materials and thicknesses of the lower electrode 12b, lower piezoelectric layer 15a, upper piezoelectric layer 15b, and upper electrode 16b in the piezoelectric thin film resonator 11b used in Experiment 2 are the same as the lower electrode 12a in the piezoelectric thin film resonator 11a used in Experiment 1, The material and thickness of the lower piezoelectric layer 15a, the upper piezoelectric layer 15b, and the upper electrode 16a are the same. No insertion membrane 20b is provided. The resonant frequency is approximately 2.4 GHz.

FIG. 9(a) is a diagram showing the resonance frequency versus time of the piezoelectric thin film resonator in Experiment 2. The horizontal axis represents the temperature inside the chamber in which the piezoelectric thin film resonator 11b is placed. The vertical axis is the resonant frequency of the piezoelectric thin film resonator. The black circles are measurement points, and the straight lines are points connecting the black circles.

As shown in FIG. 9(a), as the temperature rises, the resonant frequency decreases linearly. The amount of change in the resonance frequency with respect to temperature is proportional to the amount of change in the elastic constant of the piezoelectric layer 14b with respect to temperature. Since the elastic constant of the piezoelectric layer 14b changes approximately linearly with respect to temperature, the resonance frequency changes approximately linearly with temperature. In the example of FIG. 9(a), the amount of change in the resonant frequency with respect to temperature is -80 kHz/°C, and the amount of change in temperature when the resonant frequency changes is -0.0000125°C/Hz. Since the resonant frequency can be measured with high precision, temperature can be detected with high precision.

[Simulation: Temperature control using heat generating line]
The temperature of the heat generating line 30 when a current was passed through the heat generating line 30 was analyzed using a thermal analysis simulation. The simulated structure is shown below. Substrate 10 is a silicon substrate. Insulating layer 32 is a silicon oxide layer with a thickness of 285 nm. The heat generating line 30 is a chromium layer with a thickness of 10 nm and a platinum layer with a thickness of 300 nm from the insulating layer 32 side. The planar shape of the heating line 30 is meandering as shown in FIG. Six lines each having a length of 200 μm were arranged in the X direction, and the ends of the six lines were connected to form a meandering pattern. The width of the line is 20 μm, and the spacing between the lines is 20 μm.

FIG. 9(b) is a diagram showing the temperature with respect to the current of the heating line in the simulation. The horizontal axis is the current value flowing through the heat generating line 30, and the vertical axis is the temperature of the heat generating line 30. As shown in FIG. 9(b), as the current value flowing through the heating line 30 increases, the temperature of the heating line 30 increases, but the slope of the temperature with respect to the current is gentle, and by controlling the current of the heating line 30 , the temperature of the piezoelectric thin film resonator 11a can be controlled. Even if the heating line 30 without a cooling mechanism is used as the heater 31, the sensor 40 is cooled by the atmosphere around the sensor 40. Therefore, the temperature of the piezoelectric thin film resonator 11a can be sufficiently controlled using the heating line 30. A Peltier element or the like having a cooling function may be provided on the substrate 10 separately from the heater 31. Thereby, the accuracy of temperature control can be improved.

[Features of Example 1]
According to the first embodiment, as shown in FIGS. 2 and 3(a), on the same substrate 10, a piezoelectric thin film resonator 11a is used as a detection element for detecting changes in the environment, and a piezoelectric thin film resonator is used as a detection element for detecting temperature. A heating line 30 is provided as a heater 31 that heats the container 11b and the substrate 10. Heat generated in heater 31 is transmitted to piezoelectric thin film resonators 11a and 11b via substrate 10. Piezoelectric thin film resonators 11a and 11b have substantially the same structure. Therefore, piezoelectric thin film resonators 11a and 11b are heated to approximately the same temperature. Therefore, by detecting the temperature based on the resonance frequency of the piezoelectric thin film resonator 11b, the temperature of the piezoelectric thin film resonator 11a can be accurately controlled. Further, by providing the piezoelectric thin film resonators 11a, 11b and the heater 31 on the same substrate 10, the sensor 40 can be made smaller. Furthermore, temperature detection accuracy can be improved by using the piezoelectric thin film resonator 11b as a temperature element.

As shown in FIGS. 2 and 3(a), the heating line 30 is provided adjacently between the piezoelectric thin film resonators 11a and 11b. That is, no other elements are provided between the piezoelectric thin film resonators 11a and 11b and the heating line 30. As a result, heat is efficiently transferred from the heating line 30 to the piezoelectric thin film resonators 11a and 11b via the substrate 10, and the temperatures of the piezoelectric thin film resonators 11a and 11b become almost the same, so that the temperature of the piezoelectric thin film resonator 11a can be adjusted accurately. Can be well controlled.

In the piezoelectric thin film resonator 11a, the temperature of the sensitive film 18 affects the detection of changes in the environment, and in the piezoelectric thin film resonator 11b, the temperature of the piezoelectric layer 14b in the resonance region 50b affects the resonance frequency. Therefore, it is preferable that the heating line 30 efficiently heats the piezoelectric layers 14a and 14b in the resonance regions 50a and 50b. Therefore, the resonant region 50a has a heating line in the direction (+X direction) that intersects the direction in which the lower electrode 12a is drawn out from the resonant region 50a (-Y direction) and the direction in which the upper electrode 16a is drawn out from the resonance region 50a (+Y direction). Adjacent to 30. The resonance region 50b is connected to the heating line 30 in a direction (+X direction) that intersects the direction in which the lower electrode 12b is drawn out from the resonance region 50b (-Y direction) and the direction in which the upper electrode 16b is drawn out from the resonance region 50b (+Y direction). Adjacent. As a result, regions 52a and 54a are not provided between the resonant region 50a and the heat generating line 30, and regions 52b and 54b are not provided between the resonant region 50b and the heat generating line 30. Therefore, the resonance regions 50a and 50b and the heat generating line 30 can be brought close to each other. Therefore, heat is efficiently transmitted from the heat generating line 30 to the resonance regions 50a and 50b via the substrate 10. Therefore, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy.

In the piezoelectric thin film resonator 11a, a gap 22a is provided under the lower electrode 12a in the resonance region 50a, and in the piezoelectric thin film resonator 11b, a gap 22b is provided under the lower electrode 12b in the resonance region 50b. In such a structure, heat is difficult to be transferred from the substrate 10 to the piezoelectric layers 14a and 14b. Therefore, as shown in FIG. 3A, the first portion 13a of the lower electrode 12a provided on the substrate 10 outside the gap 22a is made to be closest to the heating line 30 among the piezoelectric thin film resonators 11a. . The second portion 13b of the lower electrode 12b provided on the substrate 10 outside the gap 22b is positioned closest to the heating line 30 of the piezoelectric thin film resonator 11b. Note that portions 13a and 13b are portions excluding portions that connect lower electrodes 12a and 12b with the outside (for example, portions where pads 24a and 24b are formed). Thereby, the heat generated in the heat generating line 30 is transmitted to the piezoelectric layer 14a via the substrate 10 and the portion 13a, and is transmitted to the piezoelectric layer 14b via the substrate 10 and the portion 13b. Therefore, the resonance regions 50a and 50b can be heated efficiently, so that the temperatures of the resonance regions 50a and 50b are almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy.

The shortest distance La between the portion 13a and the heat generating line 30 is approximately the same as the shortest distance Lb between the portion 13b and the heat generating line 30. Thereby, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy. The distance La is preferably 0.5 times or more and 2 times or less of the shortest distance Lb, more preferably 0.67 times or more and 1.5 times or less, and more preferably 0.8 times or more and 1.2 times. It is more preferable that it is the following. Further, since the resonance regions 50a and 50b can be heated efficiently, the distances La and Lb are preferably equal to or less than 1 times the width of the resonance regions 50a and 50b in the X direction (the maximum width of the resonance regions 50a and 50b). , more preferably 1/2 times or less.

The shortest distance L4a between the resonant region 50a and the heat generating line 30 is approximately the same as the shortest distance L4b between the resonant region 50b and the heat generating line 30. Thereby, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy. The distance L4a is preferably 0.5 times or more and 2 times or less, more preferably 0.67 times or more and 1.5 times or less, and more preferably 0.8 times or more and 1.2 times or less than the distance L4b. It is even more preferable that there be.

FIG. 10 is a plan view of the sensor in Example 2. FIGS. 11(a) and 11(b) are a sectional view taken along line AA and taken along line BB in FIG. 10, respectively. In FIG. 10, the resonance regions 50a, 50b and the heat generating line 30 are shown by cross hatching, the upper electrodes 16a, 16b, the pads 24a, 24b, 24d, 25a, 25b and 25d are shown by solid lines, the lower electrodes 12a, 12b, the sensitive film 18, The voids 22a and 22b are indicated by broken lines.

As shown in FIGS. 10 to 11(b), the piezoelectric thin film resonators 11a and 11b are provided adjacent to each other in the X direction, and no heating line 30 is provided between the resonance regions 50a and 50b. . The heating line 30a passes through the regions 52a and 52b and extends in the X direction. Pads 24d are provided at both ends of the heat generating line 30a in the X direction. In the regions 52a and 52b, an insulating layer 32 is provided on the substrate 10, and a heating line 30a is provided on the insulating layer 32. Lower electrodes 12a and 12b are provided on heating line 30a via insulating layers 28a and 28b, respectively.

The heating line 30b passes through the regions 54a and 54b and extends in the X direction. In the region 54a and the region 54b, the insulating layer 32 is provided on the substrate 10, and the heating line 30b is provided on the insulating layer 32. Piezoelectric layers 14a and 14b, upper electrodes 16a and 16b, and pads 25a and 25b are provided on heat generating line 30b, respectively. The other configurations are the same as those in Example 1, and their explanation will be omitted.

In Example 2, one heating line 30a is connected to the lower electrode 12a through the insulating layer 28a in the region 52a, and connected to the lower electrode 12b through the insulating layer 28b in the region 52b. Thereby, the heating line 30a efficiently heats the lower electrodes 12a and 12b. Heat is transferred to resonance regions 50a and 50b via lower electrodes 12a and 12b. Therefore, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy.

The shortest distance L1a between the resonant region 50a and the heat generating line 30a is approximately the same as the shortest distance L1b between the resonant region 50b and the heat generating line 30a. Thereby, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy. The distance L1a is preferably 0.5 times or more and 2 times or less, more preferably 0.67 times or more and 1.5 times or less, and more preferably 0.8 times or more and 1.2 times or less than the distance L1b. It is even more preferable that there be.

Preferably, the insulating layers 28a and 28b are made of substantially the same material and have substantially the same thickness. Thereby, the heating line 30a can heat the lower electrodes 12a and 12b to the same extent. In order to efficiently heat the lower electrodes 12a and 12b, it is preferable that the insulating layers 28a and 28b are thinner than the lower electrodes 12a and 12b.

One heating line 30b is joined to the piezoelectric layer 14a in a region 54a, and joined to the piezoelectric layer 14b in a region 54b. Thereby, the heating line 30b efficiently heats the piezoelectric layers 14a and 14b. Heat is transferred to resonance regions 50a and 50b via piezoelectric layers 14a and 14b. Therefore, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy. The heat generating lines 30a and 30b may be directly connected to the piezoelectric layers 14a and 14b, or may be connected via an insulating layer, a metal layer, or the like.

The distance L2a between the resonance region 50a and the heat generation line 30b is approximately the same as the distance L2b between the resonance region 50b and the heat generation line 30b. Thereby, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy. Distance L2a is preferably 0.5 times or more and 2 times or less of distance L2b, more preferably 0.67 times or more and 1.5 times or less, and more preferably 0.8 times or more and 1.2 times or less. It is even more preferable that there be.

[Modification 1 of Example 2]
FIG. 12 is a plan view of a sensor in Modification 1 of Embodiment 2. 13(a) and 13(b) are a sectional view taken along line AA and sectional view taken along line BB in FIG. 12, respectively, and FIG. 14 is a sectional view taken along line CC in FIG. In FIG. 12, the resonance regions 50a, 50b and the heat generating line 30 are shown by cross hatching, the upper electrodes 16a, 16b, the pads 24a, 24b, 24d, 25a, 25b and 25d are shown by solid lines, the lower electrodes 12a, 12b, the sensitive film 18, The voids 22a and 22b are indicated by broken lines.

As shown in FIGS. 12 to 13(b), pads 24a and 24b are provided on the lower electrodes 12a and 12b, respectively, in the +Y side region of the regions 52a and 52b. In the −Y side region of regions 52a and 52b, pads 24a and 24b are not provided on lower electrodes 12a and 12b, respectively, and heating line 30a is provided on lower electrodes 12a and 12b via insulating layers 28a and 28b. Each is provided.

The piezoelectric layers 14a and 14b are located on the +Y side of the lead-out regions 54a (first region) and 54b (second region) of the upper electrodes 16a and 16b (that is, on the opposite side of the resonant regions 50a and 50b with respect to the regions 54a and 54b). 56a and 56b are provided, respectively. In region 56a and region 56b, heating line 30b is provided on piezoelectric layers 14a and 14b with insulating layer 32 interposed therebetween, respectively.

In the first modification of the second embodiment, one heating line 30a is joined to the lower electrode 12a in the region 52a via the insulating layer 32, and is joined to the lower electrode 12b in the region 52b via the insulating layer 32. . Thereby, similarly to the second embodiment, the heating line 30a can efficiently heat the lower electrodes 12a and 12b.

Furthermore, one heating line 30b is joined to the piezoelectric layer 14a in the region 56a, and joined to the piezoelectric layer 14b in the region 56b. Thereby, the heating line 30b can efficiently heat the piezoelectric layers 14a and 14b as in the second embodiment. The heat generating lines 30a and 30b may be directly connected to the piezoelectric layers 14a and 14b, or may be connected via an insulating layer, a metal layer, or the like.

FIG. 15 is a cross-sectional view of the sensor in Example 3. FIG. 16 is a cross section taken along the line AA in FIG. 15. In FIG. 15, the resonance regions 50a, 50b and the heating line 30 are shown by cross hatching, the upper electrodes 16a, 16b, the pads 24a, 24b, 24d, 25a, 25b and 25d are shown by solid lines, the lower electrodes 12a, 12b, the sensitive film 18, The voids 22a and 22b are indicated by broken lines.

As shown in FIGS. 15 and 16, the heating line 30 is provided between the piezoelectric thin film resonators 11a and 11b. The heating line 30 has a meandering planar shape. The piezoelectric layer 14 has openings at the pads 24a, 24b, 24d, and 25d, and is continuously provided between the piezoelectric thin film resonators 11a and 11b. A piezoelectric layer 14 is provided on the heat generating line 30. The piezoelectric layer 14 between the piezoelectric thin film resonators 11a and 11b is a piezoelectric layer 14d. No insulating layer is provided between the substrate 10 and the heating line 30. The other configurations are the same as those in Example 1, and their explanation will be omitted.

In the structure of Example 1, heat generated in the heat generating line 30 is transmitted from the substrate 10 to the resonance regions 50a and 50b via the lower electrodes 12a and 12b provided outside the gaps 22a and 22b. On the other hand, in the third embodiment, a piezoelectric layer 14d (third piezoelectric layer) is provided on the substrate 10 between the piezoelectric thin film resonators 11a and 11b, and is provided continuously with the piezoelectric layers 14a and 14b. . Thereby, the heat generated in the heat generating line 30 is efficiently transferred to the resonance regions 50a and 50b via the piezoelectric layer 14. Therefore, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy. Note that the heat generating line 30 may be directly connected to the piezoelectric layer 14d, or may be connected to the piezoelectric layer 14d via an insulating layer or the like.

The distance L3a between the resonance region 50a and the heat generating line 30 is approximately the same as the distance L3b between the resonance region 50b and the heat generating line 30. Thereby, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy. Distance L3a is preferably 0.5 times or more and 2 times or less of distance L3b, more preferably 0.67 times or more and 1.5 times or less, and more preferably 0.8 times or more and 1.2 times or less. It is even more preferable that there be.

FIG. 17 is a plan view of the sensor in Example 4. FIG. 18(a) is a sectional view taken along line AA in FIG. 17. In FIG. 17, the heat generating line 30 is shown by cross hatching, and the resonance regions 50a and 50b are not shown by cross hatching. The upper electrodes 16a, 16b, pads 24a, 24b, 25a, 25b, and 25d are shown by solid lines, and the lower electrodes 12a, 12b, sensitive film 18, and voids 22a and 22b are shown by broken lines.

As shown in FIGS. 17 and 18(a), the heating line 30 passes over the substrate 10 in the resonance regions 50a and 50b and extends in the X direction. Insulating layers 28a and 28b are provided under the lower electrodes 12a and 12b, respectively, so that the heating line 30 and the lower electrodes 12a and 12b do not come into contact with each other. Gaps 22a and 22b are provided between the insulating layers 28a and 28b and the heating line 30, respectively. Insulating layers 28a and 28b are, for example, silicon oxide layers or silicon nitride layers. Thick insulating layers 28a and 28b impede vibration in resonant regions 50a and 50b. Therefore, it is preferable that the insulating layers 28a and 28b are thinner than the lower electrodes 12a and 12b, respectively. The other configurations are the same as those in Example 1, and their explanation will be omitted.

[Modification 1 of Example 4]
FIG. 18(b) is a cross-sectional view of a sensor in Modification 1 of Example 4. As shown in FIG. 18(b), the gaps 22a and 22b are provided in the recessed portions of the upper surface of the lower electrode 12a and the substrate 10. Lower electrodes 12a and 12b are provided inside gaps 22a and 22b. Therefore, insulating layers 28a and 28b are not provided under lower electrodes 12a and 12b. The other configurations are the same as those of the fourth embodiment, and the explanation will be omitted.

In Examples 1 to 3, the heat generated in the heat generating line 30 is conducted in the plane direction and reaches the resonance regions 50a and 50b. In this case, the cross-sectional area through which heat is conducted is small. Further, the distance between the heat generating line 30 and the resonance regions 50a and 50b is 10 μm or more. In contrast, in Modifications 1 and 2 of Example 4, the heating line 30 is provided within the gap 22a provided below the lower electrode 12a and within the gap 22b provided below the lower electrode 12b. Thereby, if the area of the heat generating line 30 within the gaps 22a and 22b is large, the heat of the heat generating line 30 can be efficiently transmitted to the lower electrodes 12a and 12b. Therefore, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy.

In order to efficiently transfer the heat of the heat generating line 30 to the lower electrodes 12a and 12b, the area of the heat generating line 30 within the resonance region 50a is preferably 1/3 or more, more preferably 1/2 or more of the area of the resonance region 50a, The area of the heating line 30 within the resonance region 50b is preferably 1/3 or more, more preferably 1/2 or more, of the area of the resonance region 50b. Furthermore, in order to efficiently transfer the heat of the heat generation line 30 to the lower electrodes 12a and 12b, the height of the gaps 22a and 22b is preferably 10 μm or less.

The area of the heat generating line 30 within the resonance region 50a and the area of the heat generating line 30 within the resonance region 50b are approximately the same. Thereby, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy. The area of the heat generating line 30 in the resonance region 50a is preferably 0.5 times or more and 2 times or less, and 0.67 times or more and 1.5 times or less, the area of the heat generating line 30 in the resonance region 50b. More preferably, it is 0.8 times or more and 1.2 times or less.

FIG. 19 is a plan view of the sensor in Example 5. In FIG. 19, the heat generating line 30 is shown by cross hatching, and the resonance regions 50a and 50b are not shown by cross hatching. The upper electrodes 16a, 16b, pads 24a, 24b, 24d, 25a, 25b, and 25d are shown by solid lines, and the lower electrodes 12a, 12b, sensitive film 18, and voids 22a and 22b are shown by broken lines.

As shown in FIG. 19, the planar shape of the heating line 30 is positive, with a portion 31a extending in the Y direction between the piezoelectric thin film resonators 11a and 11b, and a portion 31a extending in the X direction between the gaps 22a and 22b. A stretching portion 31b is provided. The piezoelectric layer 14 has openings at the pads 24a, 24b, 24d, and 25d, and is continuously provided between the piezoelectric thin film resonators 11a and 11b. A piezoelectric layer 14 is provided on a portion 31a of the heating line 30.

A portion 31b of the heating line 30 extends below the gaps 22a and 22b. The lower electrodes 12a and 12b are provided to the outside of the gaps 22a and 22b, respectively. Therefore, in order to prevent the portion 31b of the heating line 30 from coming into contact with the lower electrodes 12a and 12b, insulation similar to that shown in FIG. Layers 28a and 28b are provided. Although no current flows through the portion 31b of the heating line 30, if the thermal conductivity of the heating line 30 is made higher than the thermal conductivity of the substrate 10, the heat generated in the portion 31a will be larger than the heat conducted through the substrate 10. 31b, and is transmitted to resonance regions 50a and 50b.

Further, the portion 31a is joined to the piezoelectric layer 14d. Therefore, the heat generated in the portion 31a is conducted to the resonance regions 50a and 50b via the piezoelectric layer 14d, separately from the heat conducted through the portion 31b. Therefore, heat is efficiently transmitted from the heat generating line 30 to the resonance regions 50a and 50b. Therefore, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the resonance region 50a can be controlled with high accuracy.

FIG. 20 is a plan view of the sensor in Example 6. FIG. 21 is a sectional view taken along line AA in FIG. 20. In FIG. 20, the resonance regions 50a to 50c, the heat generating lines 30a and 30b are shown by cross hatching, the upper electrodes 16a to 16c, the pads 24a to 24d and 25a to 25d are shown by solid lines, and the lower electrodes 12a to 12c, the sensitive film 18 and the air gap 22a are shown. ~22c is indicated by a broken line.

As shown in FIGS. 20 and 21, in Example 6, the piezoelectric thin film resonators 11a to 11c are arranged on the substrate 10 in the X direction. A heating line 30a is provided between the piezoelectric thin film resonators 11a and 11b, and a heating line 30b is provided between the piezoelectric thin film resonators 11b and 11c. The piezoelectric thin film resonator 11c includes a lower electrode 12c, a piezoelectric layer 14c, an insertion film 20c, an upper electrode 16c, an insertion film 20c, a gap 22c, pads 24c and 25c, and does not include a sensitive film 18. The resonance region 50c is a region where the lower electrode 12c and the upper electrode 16c face each other with the piezoelectric layer 14c in between. The structure of the piezoelectric thin film resonator 11c is the same as the piezoelectric thin film resonator 11a except that the sensitive film 18 is not provided.

The piezoelectric thin film resonator 11c functions as a reference resonator without the sensitive film 18. The detector 42 detects a change in the environment based on a change in the difference in resonance frequency between the piezoelectric thin film resonators 11a and 11c.

As in Example 6, a piezoelectric thin film resonator 11c serving as a reference resonator is provided on a substrate 10 on which piezoelectric thin film resonators 11a, 11b and a heating line 30 are provided. Thereby, the temperature of the piezoelectric thin film resonators 11a and 11c can be controlled with high accuracy.

Example 7 and its modification 1 are examples in which the configuration of the voids is changed. FIG. 22(a) is a cross-sectional view of the sensor in Example 7. As shown in FIG. 22(a), the piezoelectric thin film resonator 11a is provided with a gap 22a penetrating the substrate 10. As shown in FIG. The lower electrode 12a within the resonant region 50a is provided on the air gap 22a. Although not shown, a void 22b penetrating the substrate 10 is also provided in the piezoelectric thin film resonator 11b. The lower electrode 12a within the resonant region 50b is provided above the air gap 22b. The other configurations are the same as in Example 1, and the explanation will be omitted.

[Modification 1 of Example 7]
FIG. 22(b) is a cross-sectional view of a sensor in Modification 1 of Example 7. As shown in FIG. 22(b), in the piezoelectric thin film resonator 11a, an acoustic reflection film 27 is formed under the lower electrode 12a in the resonance region 50a. The acoustic reflection film 27 includes films 27a with low acoustic impedance and films 27b with high acoustic impedance alternately provided. The thickness of each of the films 27a and 27b is, for example, approximately λ/4 (λ is the wavelength of the elastic wave). The number of laminated films 27a and 27b can be set arbitrarily. Although not shown, in the piezoelectric thin film resonator 11b as well, an acoustic reflection film 27 is provided below the lower electrode 12b in the resonance region 50b. The other configurations are the same as those in Example 7, and their explanation will be omitted.

As in Examples 1 to 7, the piezoelectric thin film resonator used in the sensor may be an FBAR (Film Bulk Acoustic Resonator) in which air gaps 22a and 22b are formed under the lower electrodes 12a and 12b in the resonance regions 50a and 50b. Further, as in Modification 1 of Embodiment 7, the piezoelectric thin film resonator includes an acoustic reflection film 27 that reflects elastic waves propagating through piezoelectric layers 14a and 14b below lower electrodes 12a and 12b in resonance regions 50a and 50b. An SMR (Solidly Mounted Resonator) may be used.

As in Examples 1 to 7 and variations thereof, lower electrodes 12a and 12b are made of substantially the same material and have substantially the same thickness, and piezoelectric layers 14a and 14b are made of substantially the same material. and have substantially the same thickness, and upper electrodes 16a and 16b are made of substantially the same material and have the same thickness. Thereby, the temperatures of the resonance regions 50a and 50b become almost the same, and the temperature of the piezoelectric thin film resonator 11a can be controlled with high precision. Preferably, the planar shapes of the resonance regions 50a and 50b are also substantially the same. Note that the term "substantially the same material" allows for differences in materials due to manufacturing errors. "Substantially the same thickness" allows for a difference of approximately ±10%. Substantially the same planar shape allows for a difference in area of approximately ±10%. In this case, the resonance frequencies of the piezoelectric thin film resonators 11a and 11b are almost the same. The piezoelectric layers 14a and 14b may have different thicknesses or materials, and the piezoelectric thin film resonators 11a and 11b may have different resonance frequencies.

The piezoelectric thin film resonator 11a includes an inserted film 20a as a temperature compensation film between the lower electrode 12a and the upper electrode 16a at least in the center of the resonance region 50a. This reduces the temperature dependence of the resonant frequency of the piezoelectric thin film resonator 11a. Therefore, the piezoelectric thin film resonator 11a can detect changes in the environment without depending on temperature. The piezoelectric thin film resonator 11b does not include a temperature compensation film between the lower electrode 12b and the upper electrode 16b in the center of the resonance region 50b. This increases the temperature dependence of the resonant frequency of the piezoelectric thin film resonator 11b. Therefore, the accuracy of temperature detection in the piezoelectric thin film resonator 11b is improved.

In Examples 1 to 7 and their modifications, lower electrodes 12a and 12b are formed from the same metal layer on the substrate 10, as shown in FIG. 4(c). As shown in FIGS. 4(d) and 5(b), piezoelectric layers 14a and 14b are formed from the same piezoelectric layer 14 on lower electrodes 12a and 12b, respectively. As shown in FIG. 5(c), upper electrodes 16a and 16b are formed from the same metal layer on piezoelectric layers 14a and 14b, respectively. As shown in FIG. 3(a), a sensitive film 18 is formed on the upper electrode 16a within the resonance region 50a. As shown in FIG. 6(b), a heater 31 is formed on the substrate 10. In this way, on the same substrate 10, lower electrodes 12a and 12b are formed simultaneously, piezoelectric layers 14a and 14b are formed simultaneously, and upper electrodes 16a and 16b are formed simultaneously. As a result, the temperatures of the resonance regions 50a and 50b in the piezoelectric thin film resonators 11a and 11b are approximately the same, and the temperature of the piezoelectric thin film resonator 11a can be controlled with high precision using the piezoelectric thin film resonator 11b. Furthermore, if the piezoelectric thin film resonators 11a, 11b and the heater 31 are formed from the same wafer, the piezoelectric thin film resonators 11a, 11b and the heater 31 can be formed on one substrate 10. Therefore, heat can be efficiently transferred from the heater 31 to the piezoelectric thin film resonators 11a and 11b via the substrate 10. As a result, the temperatures of the resonance region 50a of the piezoelectric thin film resonator 11a and the resonance region 50b of the piezoelectric thin film resonator 11b become approximately the same. Therefore, by controlling the heater 31 based on the resonance frequency of the piezoelectric thin film resonator 11b, the temperature of the piezoelectric thin film resonator a can be controlled with high accuracy.

As shown in FIG. 7C, a film 21b serving as a temperature compensation film is formed in a region between the lower electrode 12a and the upper electrode 16a and a region between the lower electrode 12b and the upper electrode 16b. Thereafter, as shown in FIG. 7D, the film 21b is left at least in the center of the region that will become the resonance region 50a, and the film 21b in the region that will become the resonance region 50b is removed. This allows the insertion film 20a serving as a temperature compensation film to be formed at least in the center of the resonance region 50a, and the insertion film 20b not to be formed in at least the center of the resonance region 50b.

By using the heating line 30, which is a conductor line, as the heater 31, the heater 31 can be easily formed on the substrate 10. The planar shape of the heating line 30 can be selected as appropriate, such as a meandering shape, a linear shape, or a curved shape. In addition to the heating line 30, the heater 31 may be a film-shaped heating element, a circuit that generates heat, or the like.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention as described in the claims. Changes are possible.

10 Substrate 12a-12c Lower electrode 14a-14d Piezoelectric layer 15a Lower piezoelectric layer 15b Upper piezoelectric layer 16a-16c Upper electrode 18 Sensitive film 20a- 20c Insert film 21a, 21b Film 22a-22c Gap 24a-24d, 25a, 25d Pad 27 Acoustic reflective film 28a, 28b, 32 Insulating layer 30, 30a, 30b Heat generating line 31 Heater 40 Sensor 42 Detector 44a, 44b Oscillator circuit 45a, 45b Measuring device 46 Control section 47 Calculation section 50a to 50c Resonance region 52a, 52b, 54a, 54b, 56a, 56b area

Claims (16)

1. A substrate and
   a first lower electrode provided on the substrate; a first piezoelectric layer provided on the first lower electrode; a first upper electrode provided on the first piezoelectric layer; and a first piezoelectric layer. a first resonant region in which the first lower electrode and the first upper electrode face each other with at least a portion thereof sandwiched therebetween; and a sensitive film provided on the first upper electrode in the first resonant region. a first piezoelectric thin film resonator;
   a second lower electrode provided on the substrate; a second piezoelectric layer provided on the second lower electrode; a second upper electrode provided on the second piezoelectric layer; and a second piezoelectric layer. a second piezoelectric thin film resonator comprising: a second resonance region in which the second lower electrode and the second upper electrode face each other with at least a portion of the piezoelectric thin film resonator in between;
   a heater provided on the substrate and controlled based on the resonant frequency of the second piezoelectric thin film resonator;
   A detection device comprising:
2. The detection device according to claim 1, wherein the heater is provided adjacently between the first piezoelectric thin film resonator and the second piezoelectric thin film resonator.
3. The first resonance region is adjacent to the heater in a direction intersecting a direction in which the first lower electrode is drawn out from the first resonance region and a direction in which the first upper electrode is drawn out from the first resonance region,
   The second resonance region is adjacent to the heater in a direction intersecting a direction in which the second lower electrode is drawn out from the second resonance region and a direction in which the second upper electrode is drawn out from the second resonance region. Detection device according to item 2.
4. In the first resonance region, a first gap is provided under the first lower electrode,
   In the second resonance region, a second gap is provided under the second lower electrode,
   A first portion of the first lower electrode excluding a portion provided on the first substrate outside the first gap and connecting the first lower electrode with the outside is a portion of the first piezoelectric thin film resonator. closest to the heater,
   A second portion of the second lower electrode excluding a portion provided on the second substrate outside the second gap and connecting the second lower electrode to the outside is a portion of the second piezoelectric thin film resonator. The detection device according to claim 3, which is closest to the heater.
5. The detection device according to claim 4, wherein the shortest distance between the first part and the heater is 0.5 times or more and twice or less the shortest distance between the second part and the heater.
6. a third piezoelectric layer provided continuously with the first piezoelectric layer and the second piezoelectric layer on the substrate between the first piezoelectric thin film resonator and the second piezoelectric thin film resonator;
   The detection device according to claim 2, wherein the heater is provided between the substrate and the third piezoelectric layer.
7. The heater is connected to the first lower electrode in a region where the first lower electrode is drawn out from the first resonance region, and the second lower electrode is joined to the first lower electrode in a region where the second lower electrode is drawn out from the second resonance region. 2. The detection device according to claim 1, wherein the detection device is connected to two lower electrodes.
8. The heater is configured such that the first upper electrode is joined to the first piezoelectric layer in a first region drawn out from the first resonant region or in a region opposite to the first resonant region with respect to the first region, and Detection according to claim 1, wherein a second upper electrode is joined to the second piezoelectric layer in a second region drawn out from the second resonant region or in a region opposite to the second resonant region with respect to the second region. Device.
9. In the first resonance region, a first gap is provided under the first lower electrode,
   In the second resonance region, a second gap is provided under the second lower electrode,
   The detection device according to claim 1, wherein the heater is provided within the first gap and the second gap.
10. The first lower electrode and the second lower electrode are made of substantially the same material and have substantially the same thickness, and the first piezoelectric layer and the second piezoelectric layer are made of substantially the same material. and having substantially the same thickness, and wherein the first upper electrode and the second upper electrode are made of substantially the same material and have substantially the same thickness. Detection device described in Section.
11. Any one of claims 1 to 9, wherein the shortest distance between the first resonance region and the heater is at least 0.5 times and at most twice the shortest distance between the second resonance region and the heater. The detection device according to item (1).
12. The first piezoelectric thin film resonator includes a temperature compensation film between the first lower electrode and the first upper electrode in at least a central portion of the first resonance region,
    10. The second piezoelectric thin film resonator does not include a temperature compensation film between the second lower electrode and the second upper electrode in a central portion of the second resonance region. The detection device described.
13. The detection device according to any one of claims 1 to 9, wherein the heater is a conductor line provided on the substrate.
14. Any one of claims 1 to 9, further comprising a detector that detects changes in the environment based on the resonant frequency of the first piezoelectric thin film resonator and controls the heater based on the resonant frequency of the second piezoelectric thin film resonator. Detection device according to item 1.
15. forming a first lower electrode and a second lower electrode from the same metal layer on the substrate;
    forming a first piezoelectric layer and a second piezoelectric layer from the same piezoelectric layer on the first lower electrode and the second lower electrode, respectively;
    a first piezoelectric thin film resonator having a first resonance region in which the first lower electrode and the first upper electrode face each other with at least a portion of the first piezoelectric layer sandwiched therebetween; on the first piezoelectric layer and the second piezoelectric layer, respectively, so that a second piezoelectric thin film resonator having a second resonance region in which the second lower electrode and the second upper electrode face each other is formed. forming a first upper electrode and the second upper electrode from the same metal layer;
    forming a sensitive film on the first upper electrode in the first resonance region;
    A method for manufacturing a detection device, comprising the step of forming, on the substrate, a heater that is controlled based on the resonance frequency of the second piezoelectric thin film resonator.
16. forming a temperature compensation film between the first lower electrode and the first upper electrode and between the second lower electrode and the second upper electrode;
    leaving the temperature compensation film at least in the center of the first resonance region and removing the temperature compensation film at least in the center of the second resonance region;
    16. The method for manufacturing a detection device according to claim 15.
    

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