JP7679352B2 - Sensor device and method for manufacturing same - Google Patents

Description

The present invention relates to a sensor device that uses a piezoelectric thin-film resonator such as an FBAR (Film Bulk Acoustic Resonator) and a method for manufacturing the same.

FBARs are piezoelectric thin-film resonators used in filters and duplexers for mobile communication devices. Development of odor sensors is underway to detect frequency changes corresponding to mass changes by applying a sensitive film that adsorbs specific gases to piezoelectric resonators such as FBARs, QCMs (Quartz Crystal Microbalances), and SAWs (Surface Acoustic Waves) (see Non-Patent Document 1).

Matthew L. Johnston, Columbia University, New York, NY, USA MEMS 2012, Paris, FRANCE, 29 January - 2 February 2012 846-849

A piezoelectric resonant sensor is typically constructed by mounting a sensor device on a circuit board that has an oscillator circuit mounted thereon. However, depending on the mounting form of the sensor device on the circuit board, it may not oscillate at its original resonant frequency and may not function as a sensor.
For example, when connecting a sensor device and a circuit board by wire bonding, if the inductance of the bonding wire increases, the dielectric region of the resonance characteristics becomes wider, raising concerns that oscillation may occur at a frequency other than the original oscillation frequency.

In view of the above circumstances, the object of the present invention is to provide a sensor device and a manufacturing method thereof that can ensure stable oscillation characteristics of a piezoelectric resonant device.

In order to achieve the above object, a sensor apparatus according to one embodiment of the present invention includes a circuit board and a plurality of sensor devices.
The multiple sensor devices each have a support substrate, a piezoelectric film provided on the support substrate, a lower electrode and an upper electrode facing each other across at least a portion of the piezoelectric film, and a sensitive film provided on the upper electrode, and are flip-chip connected to the circuit board.
The circuit board has a through hole extending along an arrangement direction of the plurality of sensor devices so as to face the sensitive films of the plurality of sensor devices and through which a gas to be detected flows.
In order to achieve the above object, a sensor apparatus according to one embodiment of the present invention includes a circuit board and a plurality of sensor devices.
The multiple sensor devices each have a support substrate, a piezoelectric film provided on the support substrate, a lower electrode and an upper electrode facing each other across at least a portion of the piezoelectric film, and a sensitive film provided on the upper electrode, and are flip-chip connected to the circuit board.
The circuit board has a recessed portion extending along an arrangement direction of the plurality of sensor devices so as to face the sensitive films of the plurality of sensor devices and through which a gas to be detected flows.

In the above sensor device, the sensor device is mounted on the circuit board using a flip-chip connection method, thereby shortening the wiring length between the sensor device and the circuit board, thereby ensuring stable oscillation characteristics of the sensor device.

The sensitive films of the plurality of sensor devices may be made of different materials.

The sensitive film may be provided in a resonance region of the upper electrode where the lower electrode and the upper electrode face each other across the piezoelectric film.

The piezoelectric film, the lower electrode and the upper electrode may have a convex curved shape in the resonance region that forms a gap between the supporting substrate and the lower electrode.

The circuit board may have a first electrode connected to the lower electrode and a second electrode connected to the upper electrode.
The sensor device may further include junctions provided on the lower electrode and the upper electrode, respectively, and electrically connected to the first electrode and the second electrode, respectively.

The joint may be a solder bump, a gold bump or an anisotropic conductive film.

The sensitive film may be an inorganic film, an organic polymer film or an organic dye film.

The sensitive membrane may be a cellulose-based resin, a fluororesin, an acrylic resin or a conductive polymer.

A method for manufacturing a sensor device according to one embodiment of the present invention includes:
a sensor device is provided in which a plurality of sensor devices, each of which has a support substrate, a piezoelectric film provided on the support substrate, a lower electrode and an upper electrode opposed to each other with at least a part of the piezoelectric film therebetween , and a sensitive film provided on the upper electrode, are flip-chip connected to a circuit substrate;
The sensor device is provided on a motherboard ;
The circuit board has a through hole extending along an arrangement direction of the plurality of sensor devices so as to face the sensitive films of the plurality of sensor devices and through which a gas to be detected flows.
A method for manufacturing a sensor device according to one embodiment of the present invention includes:
a sensor device is provided in which a plurality of sensor devices, each of which has a support substrate, a piezoelectric film provided on the support substrate, a lower electrode and an upper electrode opposed to each other with at least a part of the piezoelectric film therebetween, and a sensitive film provided on the upper electrode, are flip-chip connected to a circuit substrate;
The sensor device is provided on a motherboard;
The circuit board has a recessed portion extending along an arrangement direction of the plurality of sensor devices so as to face the sensitive films of the plurality of sensor devices and through which a gas to be detected flows.
The sensitive films of the plurality of sensor devices may be made of different materials.

According to the present invention, stable oscillation characteristics of a piezoelectric resonator device can be ensured.

1 is a side cross-sectional view illustrating a schematic configuration of a sensor device according to an embodiment of the present invention. FIG. 2 is a plan view of the sensor device. 3A and 3B are diagrams showing the configuration of a sensor device in the sensor apparatus, where (a) is a plan view and (b) is a cross-sectional view taken along line AA in (a). 3A to 3C are cross-sectional views illustrating steps in a method for manufacturing the sensor device. FIG. 11 is a side cross-sectional view showing a modified example of the configuration of the sensor device. FIG. 11 is a side cross-sectional view showing a sensor device of a comparative example. 4 is an equivalent circuit diagram of a sensor device according to an embodiment and a sensor device according to a comparative example. 11 is a simulation result showing an example of frequency characteristics of the sensor device of the embodiment and the sensor device of the comparative example.

Below, an embodiment of the present invention is described with reference to the drawings.

[Sensor device]
Fig. 1 is a side cross-sectional view showing a schematic configuration of a sensor device 1 according to an embodiment of the present invention, and Fig. 2 is a plan view of the sensor device 1. The sensor device 1 includes a circuit board 50 and a sensor device 100 mounted on the circuit board 50.

The sensor device 1 is for identifying (detecting) the type of gas or measuring the amount of the gas. In this embodiment, multiple sensor devices 100 are mounted on a circuit board 50, and each sensor device 100 is typically configured to be able to detect a different gas individually. The number of sensor devices 100 is not limited to multiple, and may be single. Details of the circuit board 50 and the implementation form of the sensor device 100 will be described later.

(Configuration of sensor device)
The configuration of the sensor device 100 will be described. A drive circuit 54 including an oscillator circuit for driving each sensor device 100 is mounted on the circuit board 50. The drive circuit 54 is configured in common to each sensor device 100, but a plurality of oscillator circuits are provided corresponding to each sensor device 100.

Next, the sensor device 100 will be described in detail. Figure 3 shows the configuration of the sensor device 100, where (a) is a plan view and (b) is a cross-sectional view taken along line A-A in (a).

The sensor device 100 of this embodiment is configured as an FBAR type piezoelectric resonator having a support substrate 10, a piezoelectric film 22, a lower electrode 21 and an upper electrode 23 facing each other across at least a portion of the piezoelectric film 22, and further having a sensitive film 30 provided at a position corresponding to the resonance region 24 of the upper electrode 23.

The support substrate 10 may be, for example, a semiconductor substrate such as a silicon (Si) substrate or a gallium arsenide (GaAs) substrate, or a ceramic substrate such as a quartz substrate, a glass substrate, or an alumina substrate.

The lower electrode 21 is formed in a predetermined shape on the support substrate 10. Here, the lower electrode 21 is formed in a polygonal shape in which the width dimension along the vertical direction of FIG. 3(a) increases toward the resonance region 24. The thickness of the lower electrode 21 is, for example, 240 nm. The lower electrode 21 is composed of a metal single layer film of aluminum (Al), copper (Cu), chromium (Cr), molybdenum (Mo), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), or iridium (Ir), or a laminate film in which multiple materials are selected from these materials.

The piezoelectric film 22 is formed in a predetermined shape on the support substrate 10 so as to cover a part of the lower electrode 21. Here, the piezoelectric film 22 is formed in a polygonal shape in which the width dimension along the vertical direction in FIG. 3(a) increases toward the resonance region 24, similar to the lower electrode 21. The thickness of the piezoelectric film 22 is, for example, 500 nm. The piezoelectric film 22 is composed of a piezoelectric body mainly composed of aluminum nitride (AlN) with the main axis in the (002) direction. In addition to an AlN film, for example, a ZnO film can be used for the piezoelectric film 22.

The upper electrode 23 is formed in a predetermined shape on the support substrate 10 so as to cover at least a portion of the piezoelectric film 22. Here, the upper electrode 23 is formed in a polygonal shape whose width dimension in the vertical direction of FIG. 3(a) increases toward the resonance region 24, similar to the lower electrode 21 and the piezoelectric film 22. The thickness of the upper electrode 23 is, for example, 240 nm. The upper electrode 23 is composed of a single layer film of the metal materials listed for the lower electrode 21, or a laminated film in which multiple materials are selected from these.

The sensor device 100 has a resonance region 24. The resonance region 24 is a region where the lower electrode 21 and the upper electrode 23 overlap. In the resonance region 24, a gap G is provided between the support substrate 10 and the lower electrode 21. In this embodiment, in the resonance region 24, the piezoelectric film 22, the lower electrode 21, and the upper electrode 23 are convex curved surfaces that form a gap G between the support substrate 10 and the lower electrode 21. The planar shape of the convex curved surface of the upper electrode 23 is, for example, an approximately elliptical shape with a major axis of 270 μm and a minor axis of 180 μm. The resonance region 24 is a region that resonates in a thickness longitudinal vibration mode when an AC voltage of a resonance frequency is input between the lower electrode 21 and the upper electrode 23. The resonance frequency of the resonance region 24 is not particularly limited, and is typically a frequency in the GHz band, and is 2.4 GHz in this embodiment.

The planar shape of the resonance region 24 may be formed into other shapes, such as a circle or a polygon having five or more sides. In particular, by making the planar shape of the resonance region 24 an ellipse or a polygon having five or more sides, the occurrence of a vibration mode propagating laterally can be suppressed more than when the planar shape of the resonance region 24 is rectangular (square or oblong), so that good resonance characteristics can be maintained.

In the resonance region 24, the gap G is a dome-shaped bulge formed between the flat upper surface of the support substrate 10 and the lower electrode 21. The dome-shaped bulge is, for example, a bulge in which the height of the gap G is low around the periphery of the gap G and the height of the gap G increases toward the inside of the gap G. An introduction path 25 is provided below the lower electrode 21 and is formed by introducing an etchant when forming the gap G. The tip of the introduction path 25 is not covered by the piezoelectric film 22 or the like, and the tip of the introduction path 25 is a hole 26. The two holes 26 are an introduction port for introducing an etchant when forming the gap G, and also an exhaust port.

The position where the hole 26 is formed is not particularly limited, but is preferably provided near the resonance region 24. After the gap G is formed, the hole 26 is blocked with an appropriate material, such as resin, adhesive, or the constituent material of the sensitive film 30. This blocks communication between the gap G and the outside air, thereby preventing deterioration of the resonance characteristics due to gas entering the gap G.

The sensitive film 30 is made of a material capable of adsorbing the gas to be detected. The material constituting the sensitive film can be selected arbitrarily depending on the type of gas to be detected, and typically, an organic polymer film (organic polymer film, organic low molecular weight film), an organic dye film, an inorganic film, or the like can be used. More specifically, the sensitive film 30 can be made of a cellulose-based resin, a fluorine-based resin, an acrylic resin, or a conductive polymer, but is not limited to these. The sensitive film 30 can be formed by dissolving the material of the sensitive film in a solvent and applying it, as well as by deposition, sputtering, or CVD (Chemical Vapor Deposition).

Examples of organic polymer materials that can be used include homopolymers having a single structure such as polystyrene, polymethyl methacrylate, 6-nylon, cellulose acetate, poly-9,9-dioctylfluorene, polyvinyl alcohol, polyvinylcarbazole, polyethylene oxide, polyvinyl chloride, poly-p-phenylene ether sulfone, poly-1-butene, polybutadiene, polyphenylmethylsilane, polycaprolactone, polybisphenoxyphosphazene, and polypropylene, copolymers which are copolymers of two or more types of homopolymers, and blend polymers which are mixtures of these.

For example, examples of organic low molecular weight materials that can be used include tris(8-quinolinolato)aluminum (Alq3), naphthyldiamine (α-NPD), BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), CBP (4,4'-N,N'-dicarbazole-biphenyl), copper phthalocyanine, fullerene, pentacene, anthracene, thiophene, Ir(ppy(2-phenylpyridinato)) ₃ , triazine thiol derivatives, dioctylfluorene derivatives, tetracontane, and parylene.

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

As shown in FIG. 3, the sensitive film 30 is selectively provided in the resonance region 24. In this embodiment, the sensitive film 30 is provided in the resonance region 24 of the upper electrode 23, and is typically provided in a portion on the upper electrode 23 that corresponds to the resonance region 24. The portion that corresponds to the resonance region 24 refers to the elliptical dome-shaped surface of the upper electrode 23, and the sensitive film 30 is provided on the convex curved surface of the upper electrode 23. The resonance region 24 is formed in an elliptical shape having substantially the same major and minor axes as the dome portion. The thickness of the sensitive film 30 is not particularly limited and can be set arbitrarily depending on the ease of adsorption or desorption of the gas to be detected, for example, 250 μm.

The sensitive film 30 is a coating containing the above-mentioned polymer material, which is selectively applied to the resonance region 24 using a mask material (not shown) and dried. Depending on the opening accuracy or position accuracy of the mask, the sensitive film 30 may be formed in an area wider or narrower than the resonance region 24, or may be provided at a position offset from the resonance region.

In a sensor device 100 in which multiple sensor devices 100 are mounted on a circuit board 50 as in this embodiment, the sensitive film 30 of each sensor device 100 is typically made of a different material. This makes it possible for a single sensor device 100 to detect multiple types of gas species.

(Method of manufacturing a sensor device)
Next, a method for manufacturing the sensor device 100 of this embodiment will be described.

4(a), a sacrificial layer 40 is formed on a support substrate 10 by, for example, sputtering, deposition, or chemical vapor deposition (CVD). The sacrificial layer 40 may be, for example, a magnesium oxide (MgO) film, and is provided to include at least the region where the gap G is formed. The thickness of the sacrificial layer 40 is, for example, about 20 nm.

Next, for example, sputtering is performed under an argon (Ar) gas atmosphere to form a metal film on the support substrate 10 and the sacrificial layer 40. The metal film may be formed by vapor deposition or CVD. The metal film is selected from at least one of the materials listed for the lower electrode 21 (Al, Cu, Cr, Mo, W, Ta, Pt, Ru, Rh, or Ir). Then, for example, photolithography and etching are used to form the metal film into a desired shape to form the lower electrode 21. At this time, a part of the lower electrode 21 is made to cover the sacrificial layer 40. The lower electrode 21 may be formed by a lift-off method.

4(b), a piezoelectric film 22 made of an AlN film is formed on the support substrate 10 and the lower electrode 21. The piezoelectric film 22 can be formed by a single-target sputtering method using an aluminum metal target in an atmosphere containing nitrogen (e.g., an atmosphere of a mixed gas of nitrogen and a rare gas (e.g., Ar)).

Next, for example, sputtering is performed under an Ar gas atmosphere to form a metal film on the piezoelectric film 22. The metal film may be formed by evaporation or CVD. As described above, the metal film is also selected from at least one of Al, Cu, Cr, Mo, W, Ta, Pt, Ru, Rh, and Ir.

Then, as shown in FIG. 4(c), the metal film is shaped into the desired shape using photolithography and etching to form the upper electrode 23. The upper electrode 23 may be formed by a lift-off method. Next, the piezoelectric film 22 is shaped into the desired shape using, for example, photolithography and etching. Furthermore, the lower electrode 21 and the sacrificial layer 40 are selectively etched to form a hole 26 (see FIG. 3(a)).

Next, as shown in FIG. 4(d), an etchant is introduced through the hole 26 to etch the sacrificial layer 40. Here, the stress of the laminated film of the lower electrode 21, the piezoelectric film 22, and the upper electrode 23 is set to be a compressive stress in advance. As a result, when the etching of the sacrificial layer 40 is completed, the laminated film swells, and a resonance region 24 having a dome-shaped bulging gap G is formed between the support substrate 10 and the lower electrode 21. In addition, an introduction path 25 connecting the gap G and the hole 26 is also formed. Then, a sensitive film 30 is provided at a portion corresponding to the resonance region 24 on the upper electrode 23, thereby producing the sensor device 100 shown in FIG. 1.

The sensitive film 30 may be formed, for example, by dissolving a cellulose-based resin, a fluorine-based resin, an acrylic resin, or a conductive polymer in a solvent such as acetone, methanol, ethanol, toluene, THF, MEK, NMP, heptane, water, etc. Although liquids other than those mentioned above may be used, among the above liquids, the solvents are preferable in that they have relatively high volatility, so that the sensitive film 30 dries easily and a uniform film can be formed.
Next, the above-mentioned dissolved sensitive film is selectively applied onto the resonance region 24 by a printing method using a metal mask or a cast-dispense method, and then dried.

(Sensor device mounting structure)
The sensor device 100 of the present embodiment configured as described above is surface mounted on the circuit board 50 by flip-chip connection. Flip-chip connection is one aspect of a surface mounting method also called a face-down method. Here, a form in which the support substrate 10 or the piezoelectric functional layer (the lower electrode 21, the piezoelectric film 22, the upper electrode 23, and the sensitive film 30) on the support substrate 10 is mounted facing the mounting surface 51 of the circuit board 50 is called flip-chip connection.

As shown in FIG. 1, one of the main surfaces of the circuit board 50 is configured as a mounting surface 51 on which the sensor device 100 is mounted. The circuit board 50 is typically a wiring board in which a wiring layer of a predetermined pattern is formed on the surface of a base material made of a rigid organic material such as a glass epoxy board. The circuit board 50 may be a multi-layer board in which multiple wiring layers are formed.

The mounting surface 51 is provided with a first electrode portion 52a electrically connected to the lower electrode 21 of the sensor device 100, and a second electrode 52b electrically connected to the upper electrode 23 of the sensor device 100. As shown in FIG. 2, one of the first electrode 52a and the second electrode 52b is connected to a drive circuit 54 via a wiring pattern 55, and the other is connected to a common ground terminal 57 via a wiring pattern 56.

The lower electrode 21 and the upper electrode 23 of the sensor device 100 are provided with joints 62a, 62b made of a conductive material, respectively. The joint 62a electrically connects the lower electrode 21 to the first electrode 52a of the circuit board 50, and the joint 62b electrically connects the upper electrode 23 to the second electrode 52b of the circuit board 50. The joints 62a, 62b are typically solder bumps, but other materials such as gold bumps and anisotropic conductive films can also be used.
Since FIG. 1 shows the sensor device 100 in a schematic manner, the joints 62a and 62b are different in size from each other, but in reality they are almost the same size (the same applies to FIG. 5).

When the joints 62a, 62b are formed by solder bumps, the sensor device 100 is mounted on the circuit board 50 by a reflow soldering method. In this case, a plurality of sensor devices 100 can be mounted on the circuit board 50 at once.
Furthermore, when the bonding portions 62a, 62b are formed of gold bumps, the sensor device 100 is mounted on the circuit board 50 by a welding method that combines ultrasonic waves and thermocompression bonding.
Furthermore, when the bonding portions 62a and 62b are made of anisotropic conductive film, the sensor device 100 is mounted on the circuit board 50 by a pressure and heat method.

The positions and number of the joints 62a and 62b are not particularly limited and can be set arbitrarily according to the shape and size of the electrodes. For example, the joints 62a and 62b may be provided at multiple locations on the lower electrode 21 and the upper electrode 23, respectively.

A recess 53 is provided on the mounting surface 51 of the circuit board 50. The recess 53 is provided in a region between the first electrode 52a and the second electrode 52b where the sensitive film 30 of the sensor device 100 faces. The recess 53 is configured as a flow path through which the gas to be detected flows, or as a reservoir for the gas.

In this embodiment, the recess 53 is composed of a groove formed linearly along the arrangement direction of the sensor device 100, as shown in FIG. 2, for example. Here, the recess 53 is provided linearly between the gas inlet 53a formed near one side of the circuit board 50 and the gas outlet 53b provided near the other opposing side. The multiple sensor devices 100 are arranged adjacent to each other so as to close the recess 53. This allows one recess 53 to be shared by multiple sensor devices 100. Of course, the recess 53 is not limited to the example in which it is provided in common for multiple sensor devices 100, and may be provided in multiple locations corresponding to each sensor device 100. In addition, instead of the recess 53, a through hole 58 provided in the circuit board 50 as shown in FIG. 5 may be used.

The multiple sensor devices 100 may be configured as a wafer-level package. In other words, the multiple sensor devices 100 may be a multi-sensor module in which multiple sensor elements each having a piezoelectric film 22, a lower electrode 21, an upper electrode 23, and a sensitive film 30 are arranged on a common support substrate 10. This allows the multiple sensor devices 100 to be mounted on the circuit board 50 all at once.

The recess 53 functions as a flow path through which gas flows. When the recess 53 is provided in common to multiple sensor devices 100 as shown in FIG. 2, the gas is caused to flow from the gas inlet 53a to the gas outlet 53b, and the components of the gas can be detected individually based on the output of each sensor device 100.

Here, depending on the mounting form on the circuit board, the piezoelectric resonant sensor device may not be able to obtain the desired sensitivity due to unstable oscillation. For example, as a comparative example, FIG. 6 shows a sensor device 2 in which a sensor device 100 is mounted on a circuit board 50 by wire bonding. In the sensor device 2, the support substrate 10 of the sensor device 100 is fixed to the mounting surface 51 of the circuit board 50 with an adhesive or the like. The lower electrode 21 and the upper electrode 23 of the sensor device 100 are electrically connected to the first electrode 52a and the second electrode 52b of the circuit board 50 via bonding wires (gold wires) W.

7(a) is an equivalent circuit of the sensor device 1 (sensor device 100) of this embodiment, and (b) is an equivalent circuit of the sensor device 2 of the comparative example. Comparing (a) and (b) of FIG. 7(a) and (b), the sensor device 2 of the comparative example differs from the sensor device 1 in that an inductor component (Lw) of the wire W is added to both ends of the sensor device 100.

Figure 8 shows simulation results showing an example of the resonance characteristics of the sensor device 1 of this embodiment and the sensor device 2 of the comparative example. In the figure, the horizontal axis is frequency (unit: Hz) and the vertical axis is impedance (unit: Ω). In the figure, waveform A1 shown by a solid line shows the resonance characteristics of the sensor device 1 of this embodiment (Figure 1), and waveform A2 shown by a dashed double-dashed line shows the resonance characteristics of the sensor device 2 of the comparative example (Figure 6).

Here, resistor R0 is 0.310709 Ω, resistor Rs is 0.345748 Ω, resistor Rp is 0.0861 Ω, capacitor Cs is 278.0687 fF, capacitor Cp is 3.803729 pF, inductor Ls is 15.7646 nH, inductor Lw is 0.47 nH, and the resonant frequency of resonance region 24 is 2.4 GHz.

8, the sensor device 2 (waveform A2) of the comparative example has an equivalent circuit in which the inductor component (Lw) of the wire W is inserted in series at both ends (lower electrode and upper electrode) of the sensor device 100. Therefore, compared to the sensor device 1 (waveform A1) of the present embodiment which does not have the inductor component (Lw), the inductive region is wider, and there is a possibility of oscillation at an unintended frequency.

In contrast, according to the sensor device 1 of this embodiment, the sharpness (Q value) of the resonance at the resonance frequency (2.4 GHz) is sharper than that of the sensor device 2, and abnormal oscillation is suppressed, resulting in stable resonance characteristics. This is because the sensor device 100 is flip-chip connected to the circuit board 50, so the wiring length between the sensor device 100 and the circuit board 50 is shortened, thereby reducing the inductor component. Furthermore, the contact area of the electrically connected portion is increased, thereby improving the reliability of the electrical connection between the sensor device 100 and the circuit board 50.

As described above, according to the sensor device 1 of this embodiment, the sensor device 100 is mounted on the circuit board 50 by a flip-chip connection method, so that the wiring length between the sensor device 100 and the circuit board 50 is short, thereby ensuring stable oscillation characteristics of the sensor device.

According to this embodiment, face-down mounting eliminates the wire component in the wire bonding method, and stable oscillation characteristics can be obtained. The circuit board 50 can provide mechanical protection for the sensor when mounting the sensor device 1 on a motherboard or during the transport process. For example, some sensors have a protective cap on the reaction part (e.g., the probe). However, with face-down mounting, this cap is not necessary. The size of the through hole 58 only needs to be large enough to expose the sensitive film, and only needs to be smaller than the support substrate 10 of the sensor device 100.

Furthermore, since the recesses 53 and 58 in the circuit board 50 function as gas reservoirs, the gas with its flow fluctuations suppressed can be supplied to the sensor device 100 .
Furthermore, the gap between the mounting surface 51 of the circuit board 50 and the sensitive film 30 may become narrow, making it difficult for the gas to pass through. In this case, the problem can be solved by forcing the gas to flow. By forming the recess 58 as a through hole as shown in Figure 5, the gas can penetrate from the surface of the circuit board 50 and reach the sensor device 100 via a short path.

Note that the recess 53 is not necessarily required if the circuit board 50 is to function as a mechanical protector during mounting of the sensor device 1 on a motherboard or during the transport process. This is because the circuit board 50 covering the surface mechanically protects the electrodes and sensitive membrane of the sensor device.

By using the recess 53 or the through hole 58 as a flow path as in this embodiment, the gas can be supplied with a certain degree of stability, and the output can be stabilized.
The recesses 53 and through holes 58 are formed in the circuit board 50 mainly by laser processing or machining. In this case, the side surfaces of the recesses and through holes become rough, and in the case of a resin board, there is a problem that the detected gas is adsorbed and held on the side surfaces. In this case, if a film that does not easily adsorb gas is formed on the inner wall of the recess or the side wall of the through hole, the adsorption can be eliminated, and the next gas detection can be made more accurate.
Furthermore, if a heater, for example a heater formed by wiring on the surface or inner layer of the substrate, is provided around the recess or through hole, it becomes possible to desorb the adsorbed gas by the heat generated.

[Modification]
Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made thereto.

For example, in the above embodiment, a sensor device with an air gap structure in which a resonance region 24 is formed by forming a gap G between the support substrate 10 and the lower electrode 21 has been described as an example, but the sensor device may be configured with a cavity structure in which a cavity is provided in the support substrate 10 and the laminated region of the lower electrode, piezoelectric film, and upper electrode formed on the cavity serves as the resonance region. Alternatively, a sensor device with an acoustic reflection film structure may be adopted.

Reference Signs List 1, 3: sensor device 10: supporting substrate 21: lower electrode 22: piezoelectric film 23: upper electrode 24: resonance region 30: sensitive film 50: circuit board 51: mounting surface 52a: first electrode 52b: second electrode 62a, 62b: joint 53: recess 58: through hole 100: sensor device G: gap

Claims (12)

A circuit board;
a plurality of sensor devices each including a support substrate, a piezoelectric film provided on the support substrate, a lower electrode and an upper electrode opposed to each other with at least a part of the piezoelectric film interposed therebetween, and a sensitive film provided on the upper electrode, the sensor devices being flip-chip connected to the circuit substrate;
Equipped with
The circuit board is disposed along an arrangement direction of the plurality of sensor devices so as to face the sensitive films of the plurality of sensor devices, and has a through hole through which a gas to be detected flows . A circuit board;
a plurality of sensor devices each including a support substrate, a piezoelectric film provided on the support substrate, a lower electrode and an upper electrode opposed to each other with at least a part of the piezoelectric film interposed therebetween, and a sensitive film provided on the upper electrode, the sensor devices being flip-chip connected to the circuit substrate;
Equipped with
The circuit board is disposed along an arrangement direction of the plurality of sensor devices so as to face the sensitive films of the plurality of sensor devices, and has a recess through which a gas to be detected flows. The sensor device according to claim 1 or 2,
The sensitive films of the plurality of sensor devices are formed of different materials.
Sensor device. The sensor device according to any one of claims 1 to 3,
The sensor device, wherein the sensitive film is provided in a resonance region of the upper electrode where the lower electrode and the upper electrode face each other with the piezoelectric film interposed therebetween. The sensor device according to claim 4,
the piezoelectric film, the lower electrode and the upper electrode have a convex curved shape that forms a gap between the support substrate and the lower electrode in the resonance region. The sensor device according to any one of claims 1 to 5,
the circuit board has a first electrode connected to the lower electrode and a second electrode connected to the upper electrode;
The sensor device further includes junctions provided on the lower electrode and the upper electrode, respectively, and electrically connected to the first electrode and the second electrode, respectively. The sensor device according to claim 6,
The sensor device, wherein the bonding portion is a solder bump, a gold bump, or an anisotropic conductive film. The sensor device according to any one of claims 1 to 6,
The sensor device, wherein the sensitive film is an inorganic film, an organic polymer film, or an organic dye film. The sensor device according to claim 8,
The sensor device, wherein the sensitive film is made of a cellulose-based resin, a fluorine-based resin, an acrylic resin, or a conductive polymer. a sensor device is provided in which a plurality of sensor devices, each of which has a support substrate, a piezoelectric film provided on the support substrate, a lower electrode and an upper electrode opposed to each other with at least a part of the piezoelectric film therebetween , and a sensitive film provided on the upper electrode, are flip-chip connected to a circuit substrate;
The sensor device is provided on a motherboard ;
The circuit board has a through hole extending along an arrangement direction of the plurality of sensor devices so as to face the sensitive films of the plurality of sensor devices and through which a gas to be detected flows.
A method for manufacturing a sensor device. a sensor device is provided in which a plurality of sensor devices, each of which has a support substrate, a piezoelectric film provided on the support substrate, a lower electrode and an upper electrode opposed to each other with at least a part of the piezoelectric film therebetween, and a sensitive film provided on the upper electrode, are flip-chip connected to a circuit substrate;
The sensor device is provided on a motherboard;
The circuit board has a recess extending along an arrangement direction of the plurality of sensor devices so as to face the sensitive films of the plurality of sensor devices and through which a gas to be detected flows. A method for manufacturing a sensor device according to claim 10 or 11, comprising the steps of:
The sensitive films of the plurality of sensor devices are formed of different materials.
A method for manufacturing a sensor device.

Images