Film bulk acoustic resonator pressure sensor with peripheral channel

Abstract

The invention discloses a film bulk acoustic resonator pressure sensor with peripheral channels, which comprises a pressure sensitive unit and a substrate unit positioned below the pressure sensitive unit, a plurality of channels with cavities are formed on the substrate unit, the plurality of channels with the cavities are adjacently arranged in a shape like a Chinese character'hui ', and the pressure sensitive unit is arranged on the substrate unit. And a plurality of micropores are formed in the upper part of each channel with the cavity. According to the invention, by designing the channel type cavity, the sensitivity and the measuring range of the pressure sensing device to the pressure are improved, and the problem that the maximum deformation quantity of the device under the action of the pressure is limited because the substrate area of the existing FBAR pressure sensor is uniform and consistent is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and particularly to a thin film bulk acoustic resonator pressure sensor with peripheral channels. Background Art

[0002] Pressure monitoring has wide applications in fields such as industrial production control, automotive and transportation, and medical and health. With the growth of the demand for miniaturization, low cost, and high-performance sensing, MEMS (Micro-Electro-Mechanical System) pressure sensors have developed rapidly. Currently, MEMS pressure sensors mainly include types such as capacitive, piezoresistive, resonant, and thin film bulk acoustic wave (FBAR) pressure sensors. Among them, FBAR pressure sensors have significant advantages over traditional MEMS pressure sensors in terms of sensitivity, power consumption, response speed, and integration.

[0003] Existing FBAR-based pressure sensors generally only include the main thin film structure of FBAR. The manufacturing process is divided into 5 steps. First, a cavity is etched on the substrate surface and then filled with silicon dioxide. Then, the bottom electrode, piezoelectric layer, and top electrode are grown respectively. Finally, the cavity filler is released, so that a cavity is formed under the device. When pressure is applied to the surface of the top electrode, the FBAR deforms. The change in the distance between the top electrode and the bottom electrode will change the wavelength of the bulk acoustic wave in the resonant cavity. At the same time, the physical properties of the piezoelectric material change under the action of stress, changing the acoustic wave velocity of the bulk acoustic wave. The changes in wavelength and wave velocity will cause the resonant frequency of the bulk acoustic wave resonator to change. By measuring the change in its resonant frequency, the magnitude of the external pressure can be characterized.

[0004] The substrate area of the existing FBAR pressure sensor is uniform, resulting in a strong fixing effect of the substrate on the resonator, limiting the maximum deformation of the device under pressure, and reducing the sensitivity and range of the device. Summary of the Invention

[0005] To solve the problem that the substrate area of the existing FBAR pressure sensor is uniform and limits the maximum deformation of the device under pressure, the present invention provides a thin film bulk acoustic resonator pressure sensor with peripheral channels, which improves the sensitivity and range of the pressure sensor device by designing a channel-type cavity.

[0006] According to one aspect of the specification of the present invention, there is provided a thin film bulk acoustic resonator pressure sensor with peripheral channels, including a pressure sensitive unit and a substrate unit located below the piezoelectric sensitive unit. A plurality of channels with cavities are formed on the substrate unit, and the plurality of channels with cavities are arranged adjacent to each other in a zigzag shape. A plurality of micropores are provided above each of the channels with cavities.

[0007] As a further technical solution, the pressure-sensitive unit includes a piezoelectric layer, a top electrode disposed above the piezoelectric layer, a bottom electrode disposed below the piezoelectric layer, a bottom cavity located below the piezoelectric layer, and a GSG measurement interface.

[0008] As a further technical solution, the top electrode, the bottom electrode, and the bottom cavity are all irregular pentagons.

[0009] As a further technical solution, a plurality of micropores are distributed above the piezoelectric sensitive unit for releasing the filler in the bottom cavity.

[0010] As a further technical solution, the plurality of micropores above the piezoelectric sensitive unit are uniformly distributed outside the five vertices of the pentagon.

[0011] As a further technical solution, the bottom cavity of the pressure-sensitive unit and the cavity of the peripheral substrate unit are formed by releasing simultaneously.

[0012] As a further technical solution, the number of the channels with cavities is related to the pressure application surface.

[0013] As a further technical solution, the radial dimension of the micropore depends on the designed channel width and the position of the GSG measurement interface.

[0014] As a further technical solution, the piezoelectric thin film of the pressure-sensitive unit uses a single-layer AlN thin film.

[0015] According to one aspect of the specification of the present invention, a method for measuring pressure is provided, which is implemented by using the thin-film bulk acoustic resonator pressure sensor with peripheral channels, and the method includes: Step 1: Measure the resonance frequency of the thin-film bulk acoustic resonator under the condition of no pressure through the GSG measurement interface as the reference frequency; Step 2: Apply different magnitudes of pressure to the thin-film bulk acoustic resonator respectively, and calibrate the resonance frequency of the thin-film bulk acoustic resonator under the pressure condition through the measurement interface; Step 3: Fit the resonance frequency of the thin-film bulk acoustic resonator with the pressure to form a pressure-resonance frequency curve.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: In the present invention, the substrate part of the pressure sensor is divided into a normal substrate area and a channel area. The channel area is manufactured in the same way as the bottom cavity of the bulk acoustic resonator, filled with silicon dioxide and then released, and the channel area and the normal substrate area are arranged adjacent to each other periodically. Since the thickness of the peripheral channel area is smaller than that of the general area, the clamping effect around the thin-film bulk acoustic resonator is reduced, and the pressure sensitivity of the thin-film bulk acoustic resonator is improved.

[0017] The present invention has the advantages of strong applicability and high detection accuracy, and can meet the pressure monitoring requirements in different scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a cross-sectional view of the pressure sensor device provided by the embodiment of the present invention.

[0020] Figure 2 It is a top view of the pressure sensor device provided by the embodiment of the present invention.

[0021] Figure 3 It is a schematic diagram of the change of the output curve of the thin film bulk acoustic resonator provided by this embodiment under pressure conditions.

[0022] In the figure: 1 - substrate unit; 2 - piezoelectric thin film; 3 - cavity; 4 - micropore; 5 - top electrode; 6 - bottom electrode; 7 - GSG test interface. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] It should be noted that: The terms "including" and "having" in the specification and claims of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0024] The block diagrams shown in the drawings are only functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices. The flowcharts shown in the drawings are only exemplary illustrations and do not necessarily include all the content and operations / steps, nor do they have to be executed in the described order. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to the actual situation.

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention. Additionally, the technical features in each embodiment or individual embodiment provided by the present invention can be combined arbitrarily with each other to form a new technical solution. Such combination is not restricted by the order of steps and / or the pattern of structural composition, but must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or inability to implement, it should be considered that such combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0026] The present invention provides a thin-film bulk acoustic resonator pressure sensor with peripheral channels, including: a pressure-sensitive unit and a substrate unit (i.e., the surrounding substrate part). The pressure-sensitive unit is an FBAR resonator, including: a bottom electrode, a top electrode, a piezoelectric layer, a bottom cavity, and a GSG measurement interface. The FBAR surrounding substrate part includes: a substrate with normal thickness and a channel part with a cavity. The channel part and the normal substrate part are both located below the piezoelectric thin film and are arranged adjacent to each other in a zigzag pattern. A plurality of micropores are distributed above the channel to facilitate the release of the channel filler in subsequent processes to form a cavity.

[0027] By designing channels in the surrounding substrate part of the FBAR resonator cavity, the present invention increases the maximum deformation of the resonant region under pressure, improving the sensitivity and measurement range of the resonator to pressure.

[0028] In an exemplary embodiment of the present invention, a bulk acoustic resonator pressure sensor with peripheral channels is provided. Figure 1 and Figure 2 are respectively a cross-sectional view and a top view of the pressure sensor according to the embodiment of the present invention. Referring to Figure 1 and Figure 2 , the pressure sensor device in this embodiment includes: Substrate unit 1; Piezoelectric layer 2 located above the bottom electrode and above the non-resonator region part; FBAR bottom cavity and FBAR surrounding substrate cavity 3; Micropores 4 (also called release holes) above the cavity region; Top electrode 5 above the piezoelectric layer in the FBAR resonant region; Bottom electrode 6 below the piezoelectric layer in the FBAR resonant region; GSG test interface 7.

[0029] Among them, the bottom electrode 6, the top electrode 5, and the piezoelectric layer together form the FBAR pressure sensing sensitive unit. The cavity part below the FBAR and the cavity part of the surrounding substrate are used to increase the deformation of the FBAR under pressure conditions and improve the device sensitivity. When pressure is applied to the FBAR and its surrounding substrate part, the FBAR will bend downward. At the same time, due to the existence of the cavity, the surrounding substrate part will also bend downward and collapse, further increasing the deformation amount of the FBAR.

[0030] In this embodiment, the FBAR top electrode, bottom electrode, and bottom cavity are all irregular pentagons to reduce the acoustic wave leakage of the FBAR.

[0031] In this embodiment, the diameter of the release hole of the FBAR bottom cavity is preferably 15 μm and is evenly distributed outside the five vertices of the pentagon.

[0032] In this embodiment, the number of release holes at the inner ring channel is 8, and the number of release holes at the outer ring channel is 12.

[0033] Preferably, the number of cavity-type channels depends on the application range of the pressure sensor. The larger the pressure application surface, the more the number of channels.

[0034] Preferably, the radial dimension of the release hole depends on the designed channel width and the position of the GSG test structure.

[0035] Preferably, the number of release holes depends on the length of the channel. In order to completely release the filling in the cavity, generally, the longer the channel, the more release holes are required.

[0036] In this embodiment, the piezoelectric layer is made of AlN thin film material, the top electrode and the bottom electrode are both made of Mo, and the cavity filling is SiO2. The metal layer sputtered on the GSG surface is used for external electrical connection. The top electrode 5 and the bottom electrode 6 of the pressure measurement structure are directly connected to the corresponding GSG interfaces, thereby transmitting the signal measured by the FBAR to the external circuit.

[0037] Those skilled in the art should be clear that in addition to the AlN thin film, other pressure-sensitive piezoelectric thin films can also be used, and other materials can also be used for the upper and lower electrode materials and the material of the sputtered layer on the GSG surface, which will not be elaborated here.

[0038] The embodiment of the present invention also provides a method for measuring pressure using FBAR. Under pressure conditions, the distance between the upper and lower electrodes of the FBAR and the characteristics of the piezoelectric material change, resulting in a change in the resonance frequency. The relationship between the FBAR resonance frequency and the structure and material characteristics is as follows:

[0039] Among them, f represents the FBAR resonance frequency, wavelength λDetermined by the distance between the upper and lower electrodes, the wave velocity v Determined by the physical properties of the piezoelectric material.

[0040] In this embodiment, the measurement process includes three steps: Step 1: Through the GSG measurement interface, measure the FABR resonance frequency under no-pressure conditions as the reference frequency.

[0041] Step 2: Apply different magnitudes of pressure to the FBAR, and calibrate the resonance frequency of the FBAR under pressure conditions through the measurement interface.

[0042] Step 3: Fit the FBAR resonance frequency with the pressure to form a pressure-resonance frequency curve.

[0043] The device calibrated by the pressure-resonance frequency curve fitting can be used for pressure tests in different application scenarios. By the resonance frequency shift, find the corresponding pressure value on the pressure-resonance frequency curve.

[0044] In summary of the above embodiments, the present invention discloses a thin-film bulk acoustic resonator pressure sensor with peripheral channels. The sensor includes a thin-film bulk acoustic resonator and the surrounding substrate part. The thin-film bulk acoustic resonator is the pressure-sensitive unit, including a bottom cavity, a top electrode, a bottom electrode, and a piezoelectric layer. When subjected to pressure, the thin-film bulk acoustic resonator is subjected to tensile or compressive stress, which in turn causes changes in the material properties of the piezoelectric layer in the resonator and the geometric dimensions of the resonator, resulting in a change in the resonance frequency of the device. The magnitude and direction of the pressure can be calibrated through the change in the resonator frequency. The substrate part is divided into a normal substrate area and a channel area. The channel area is manufactured in the same way as the bottom cavity of the bulk acoustic resonator, filled with silicon dioxide and then released. The channel area and the normal substrate area are arranged periodically adjacent to each other. Since the thickness of the peripheral channel area is less than that of the general area, the clamping effect around the thin-film bulk acoustic resonator is reduced, improving the pressure sensitivity of the thin-film bulk acoustic resonator. The present invention has the advantages of strong applicability and high detection accuracy, and can meet the pressure monitoring requirements in different scenarios.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A thin-film bulk acoustic wave resonator pressure sensor with a peripheral channel, characterized in that It includes a pressure-sensitive unit and a substrate unit located below the piezoelectric-sensitive unit. A plurality of channels with cavities are formed on the substrate unit, and the plurality of channels with cavities are arranged adjacent to each other in a zigzag shape. A plurality of micropores are provided above each of the channels with cavities.

2. The thin-film bulk acoustic resonator pressure sensor with a peripheral channel according to claim 1, characterized in that, The pressure-sensitive unit includes a piezoelectric layer, a top electrode provided above the piezoelectric layer, a bottom electrode provided below the piezoelectric layer, a bottom cavity located below the piezoelectric layer, and a GSG measurement interface.

3. The thin film bulk acoustic resonator pressure sensor with a peripheral channel according to claim 2, characterized in that, The top electrode, the bottom electrode, and the bottom cavity are all irregular pentagons.

4. The thin film bulk acoustic resonator pressure sensor with a peripheral channel according to claim 3, characterized in that, A plurality of micropores are distributed above the piezoelectric-sensitive unit for releasing the filler in the bottom cavity.

5. The thin film bulk acoustic resonator pressure sensor with a peripheral channel according to claim 4, characterized in that, The plurality of micropores above the piezoelectric-sensitive unit are uniformly distributed outside the five vertices of the pentagon.

6. The thin-film bulk acoustic resonator pressure sensor with a peripheral channel according to claim 1, characterized in that, The bottom cavity of the pressure-sensitive unit and the cavity of the peripheral substrate unit are formed by releasing simultaneously.

7. The thin film bulk acoustic resonator pressure sensor with a peripheral channel according to claim 1, characterized in that, The number of the channels with cavities is related to the pressure application surface.

8. The thin film bulk acoustic resonator pressure sensor with a peripheral channel according to claim 1, characterized in that The radial size of the micropores depends on the designed channel width and the position of the GSG measurement interface.

9. The thin film bulk acoustic resonator pressure sensor with a peripheral channel according to claim 1, characterized in that The piezoelectric thin film of the pressure-sensitive unit uses a single-layer AlN thin film.

10. A method for measuring pressure, which is implemented by using the thin-film bulk acoustic resonator pressure sensor with a peripheral channel described in any one of claims 1-9, characterized in that The method includes: Step 1: Measure the resonant frequency of the thin-film bulk acoustic wave resonator under no-pressure conditions through the GSG measurement interface as the reference frequency; Step 2: Apply different magnitudes of pressure to the thin-film bulk acoustic wave resonator respectively, and calibrate the resonant frequency of the thin-film bulk acoustic wave resonator under pressure conditions through the measurement interface; Step 3: Fit the resonant frequency of the thin-film bulk acoustic wave resonator with the pressure to form a pressure-resonant frequency curve.

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