A MEMS chip based on a uniaxial vibration sensor

Abstract

The present invention discloses a MEMS chip based on a uniaxial vibration sensor, which relates to the technical field of semiconductor processes. It includes a substrate having opposite front and back surfaces. A piezoelectric layer is provided on the front surface. The piezoelectric layer includes a bottom electrode, a piezoelectric thin film, and a top electrode that are sequentially stacked. The structure within the longitudinal projection area of the chip corresponding to the back cavity is a vibrating membrane, and the piezoelectric layer in the longitudinal projection area of the back cavity is the vibrating membrane. The piezoelectric thin film includes a piezoelectric thin film main body located in the non-vibrating membrane area, as well as a central block, a plurality of cantilever beams, and a plurality of fixed beams located in the vibrating membrane area. The central block is located at the center of the vibrating membrane area. The two ends of the fixed beam are respectively connected to the central block and the piezoelectric thin film main body. One end of the cantilever beam is connected to the central block, and the cantilever beam amplifies the force received. The present invention improves the sensitivity by the force amplification of the cantilever beam and improves the stability of the chip by the fixed beam.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor chips, and in particular to a MEMS chip based on a uniaxial vibration sensor. Background Art

[0002] As a new generation of intelligent materials, piezoelectric materials have attracted wide attention due to their mechanical-electric energy conversion performance. In recent years, with the rapid development of microelectromechanical systems (MEMS), MEMS sensor chips made of piezoelectric thin films have the advantages of miniaturization and low power consumption. And micromachined accelerometers, as important inertial devices, are widely used in various fields such as inertial navigation, acceleration measurement, medical diagnosis, health monitoring, and disaster warning.

[0003] The classical structures of piezoelectric MEMS vibration sensors mainly include cross-beam type, ring mass, and single cantilever beam. However, a typical cross-beam type accelerometer is a three-axis accelerometer, and in actual use, decoupling of the outputs in each direction is required; for the ring mass type accelerometer, due to the excessive rigidity of the thin film, the sensitivity output in the uniaxial (Z) direction is too small; although the structure of the single cantilever beam type accelerometer is simple, series and parallel connections are required to meet the high-sensitivity requirements. Summary of the Invention

[0004] To solve the technical problems existing in the background art, the present invention proposes a MEMS chip based on a uniaxial vibration sensor.

[0005] A MEMS chip based on a uniaxial vibration sensor proposed by the present invention includes a substrate, the substrate having opposite front and back surfaces, a piezoelectric layer provided on the front surface, the piezoelectric layer including a bottom electrode, a piezoelectric thin film, and a top electrode stacked in sequence, a back cavity provided on the back surface, the structure of the chip within the longitudinal projection area corresponding to the back cavity being a vibrating membrane, the part opposite to the vibrating membrane being the vibrating membrane area, and the part not opposite to the vibrating membrane being the non-vibrating membrane area;

[0006] The piezoelectric thin film includes a piezoelectric thin film main body, a central block, a plurality of cantilever beams, and a plurality of fixing beams, the piezoelectric thin film main body being located in the non-vibrating membrane area of the vibrating membrane, the central block being located in the vibrating membrane area, and the plurality of cantilever beams and the plurality of fixing beams being located outside the central block;

[0007] The central block is located at the center of the diaphragm region. One end of the fixed beam is connected to the central block, and the other end is connected to the piezoelectric film body. The cantilever beam is located between two adjacent fixed beams and forms a deformation gap with the fixed beams. One end of the cantilever beam is connected to the central block, and the other end of the cantilever beam is suspended. The cantilever beam amplifies the force it receives. Through the action of the cantilever beam to amplify the force, the sensitivity is improved, and the stability of the chip is improved through the fixed beam. At the same time, through a special electrode distribution, the positive charges on the cantilever beam and the fixed beam are collected together and fed back outwards.

[0008] Preferably, the substrate is an SOI substrate, including a bottom silicon, a buried oxide layer, and a top silicon stacked in sequence.

[0009] Preferably, the structure of the bottom electrode in the diaphragm region is the same as and corresponds to the structure of the piezoelectric film in the diaphragm region.

[0010] Preferably, the structure of the top silicon in the diaphragm region corresponds to the bottom electrode.

[0011] Preferably, the central block is a cylindrical structure, and the axis line of the central block coincides with the center line of the diaphragm region.

[0012] Preferably, the multiple cantilever beams are arranged in a circular array along the central block.

[0013] Preferably, the multiple fixed beams are arranged in a circular array along the central block.

[0014] Preferably, the number of the cantilever beams is the same as that of the fixed beams, and they are arranged in a cross pattern.

[0015] Preferably, the top electrode includes a central electrode, multiple floating electrodes arranged outside the central electrode and connected to the central electrode, an outer ring electrode, multiple fixed electrodes arranged inside the outer ring electrode and connected to the outer ring electrode, and an extraction electrode arranged outside the outer ring electrode and connected to the outer ring electrode;

[0016] The extraction electrode is located in the non-diaphragm region, and the fixed electrode is electrically connected to the central electrode;

[0017] The central electrode is arranged on the central block. The floating electrode faces the part of the cantilever beam close to the central block. The fixed electrode is connected to the part of the fixed beam far from the central block. The outer ring electrode is connected to the piezoelectric film body;

[0018] Among them, the floating electrode is used to collect the positive charges on the cantilever beam, the fixed electrode is used to collect the positive charges on the fixed beam, and the positive charges collected by the floating electrode and the fixed electrode are fed back outwards through the outer ring electrode and the extraction electrode.

[0019] Preferably, the cross-sectional area of the suspension electrode is smaller than that of the cantilever beam, and the cross-sectional area of the fixed electrode is smaller than that of the fixed beam.

[0020] In the present invention, the proposed MEMS chip based on a uniaxial vibration sensor reduces the lateral sensitivity of the chip through the high symmetry of the fixed beam and the chip itself, making the lateral sensitivity of the final vibration sensor negligible, and thus eliminating the need to decouple the received acceleration signal; meanwhile, in the MEMS chip proposed in the embodiment of the present invention, the cantilever beam uses the central block as an anchor point to act as a force amplifier to improve the longitudinal sensitivity of the chip.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the MEMS chip based on a uniaxial vibration sensor proposed in the embodiment of the present invention;

[0023] Figure 2 is Figure 1 exploded view of the structure;

[0024] Figure 3 is Figure 1 front view of;

[0025] Figure 4 is Figure 1 top view of;

[0026] Figure 5 is Figure 1 bottom view of;

[0027] Figure 6 It is a schematic diagram of the top electrode of the present invention;

[0028] Figure 7 It is a schematic diagram of the piezoelectric layer of the present invention;

[0029] Figure 8 It is a schematic diagram of the bottom electrode of the present invention;

[0030] Figure 9 It is a schematic diagram of the substrate of the present invention;

[0031] In the figure: 1. Substrate; 11. Bottom silicon; 12. Buried oxide layer; 13. Top silicon; 2. Bottom electrode; 3. Piezoelectric thin film; 31. Central block; 32. Cantilever beam; 33. Fixed beam; 34. Main body of piezoelectric thin film; 4. Top electrode; 41. Central electrode; 42. Suspension electrode; 43. Fixed electrode; 44. Outer ring electrode; 45. Lead-out electrode. Detailed implementation mode

[0032] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar symbols represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0033] As Figure 1 - Figure 2 shown, a MEMS chip based on a uniaxial vibration sensor includes a substrate 1 and a piezoelectric layer stacked in sequence, and the piezoelectric layer is disposed on the surface of the substrate 1.

[0034] A cylindrical groove is formed on the back surface of the substrate 1 as a back cavity. The structure within the longitudinal projection area of the chip corresponding to the back cavity is a diaphragm. The back cavity provides a vibration space for the diaphragm to release. The part of the chip opposite to the diaphragm is the diaphragm area, and the part of the chip not opposite to the diaphragm is the non-diaphragm area. Optionally, the substrate 1 is an SOI substrate, including a bottom silicon 11, a buried oxide layer 12, and a top silicon 13 stacked in sequence, and the back cavity penetrates through the bottom silicon 11 and the buried oxide layer 12.

[0035] The piezoelectric layer includes a bottom electrode 2, a piezoelectric thin film 3, and a top electrode 4 stacked in sequence on the front surface of the substrate.

[0036] As Figure 7 shown, the structure of the piezoelectric thin film 3 is formed by etching. The piezoelectric thin film includes a piezoelectric thin film main body 34 located in the non-diaphragm area, a central block 31, a plurality of cantilever beams 32, and a plurality of fixed beams 33 located in the diaphragm area. The central block 31 is located at the center of the diaphragm area and has a cylindrical structure. The axis line of the central block 31 coincides with the center line of the diaphragm area. The plurality of cantilever beams 32 and the plurality of fixed beams 33 are circumferentially distributed outside the central block 31, and the axis line of the central block 31 coincides with the axis line of the diaphragm. The two ends of the fixed beam 33 are respectively connected to the central block 31 and the piezoelectric thin film main body 34, that is, the fixed beam 33 connects the central block 31 and the piezoelectric thin film main body 34. One end of the cantilever beam 32 is connected to the central block 31, and the other end (i.e., the end of the cantilever beam 32 away from the central block 31) is suspended and not connected to the piezoelectric thin film main body 34. Optionally, the number of the fixed beams 33 and the cantilever beams 32 is the same and they are arranged in a cross pattern. The plurality of cantilever beams 32 are arranged in a circular array along the central block 31, and the plurality of fixed beams 33 are arranged in a circular array along the central block 31, that is, there is a cantilever beam 32 between any two adjacent groups of fixed beams 33, and a deformation gap is formed between the cantilever beam 32 and the fixed beam 33.

[0037] The structure of the bottom electrode 2 within the diaphragm area corresponds to that of the piezoelectric thin film 3;

[0038] The structure at the top of the top silicon 13 of the substrate 1 within the diaphragm area is the same as and corresponds to that of the bottom electrode 2 (as Figure 9as shown).

[0039] The central block 31 can replace the mass block part of the traditional chip, improving the sensitivity of the diaphragm vibration. There are two aspects to improving the performance of the vibration sensor. On the one hand, it is to reduce the sensitivity of the chip in the x and y axes (i.e., the lateral sensitivity), and on the other hand, it is to improve the sensitivity of the chip in the z axis (i.e., the longitudinal sensitivity). The MEMS chip proposed in the embodiment of the present invention reduces the lateral sensitivity of the chip through the fixed beam 33 and the high symmetry of the chip itself, making the lateral sensitivity of the final vibration sensor negligible, and thus there is no need to decouple the received acceleration signal. At the same time, in the MEMS chip proposed in the embodiment of the present invention, the cantilever beam 32 uses the central block 31 as an anchor point and acts as a force amplifier to improve the longitudinal sensitivity of the chip.

[0040] Such as Figure 6As shown, the top electrode 4 includes a central electrode 41, a plurality of floating electrodes 42, a plurality of fixed electrodes 43, an outer ring electrode 44, and a lead-out electrode 45. The central electrode 41 is disposed on the surface of the central block 31. The central electrode 41 has a cylindrical structure, and the axis line of the central electrode 41 coincides with the axis line of the central block 31. The number of floating electrodes 42 is the same as the number of cantilever beams 32. One floating electrode 42 is disposed on each cantilever beam 32, and the plurality of floating electrodes 42 are arranged in a circular array along the central electrode 41. The cross-sectional area of the floating electrode 42 is smaller than the cross-sectional area of the cantilever beam 32, and the floating electrode 42 is located at a position on the cantilever beam 32 close to the central block 31. One end of the floating electrode 42 close to the central block 31 is connected to the central block 31. The number of fixed electrodes 43 is the same as the number of fixed beams 33. One fixed electrode 43 is disposed on each fixed beam 33, and the plurality of fixed electrodes 43 are arranged in a circular array along the central electrode 41. The cross-sectional area of the fixed electrode 43 is smaller than the cross-sectional area of the fixed beam 33, and the fixed electrode 43 is located at a position on the fixed beam 33 far from the central block 31. The fixed electrodes 43a and 43b that are centrosymmetric among the plurality of fixed electrodes 43 are both electrically connected to the central electrode 41. The outer ring electrode 44 has an annular structure, and the axis line of the outer ring electrode 44 coincides with the center line of the diaphragm region. The inner diameter of the outer ring electrode 44 is larger than the diameter of the diaphragm region. Each fixed electrode 43 is electrically connected to the outer ring electrode 44. The lead-out electrode 45 is located in the non-diaphragm region and in a region outside the longitudinal projection area of the outer ring electrode 44. The outer ring electrode 44 is electrically connected to the lead-out electrode 45. When the diaphragm receives a signal excitation in the z-axis direction (i.e., the longitudinal direction), according to solid mechanics, the bending moments received by the cantilever beam 32 and the fixed beam 33 have positive and negative values. Manifested on the piezoelectric vibration sensor, positive and negative charges are generated. The settings of the floating electrode 42 and the fixed electrode 43 enable the floating electrode 42 to collect the positive charges generated by the bending moment of the cantilever beam 32, and enable the fixed electrode 43 to collect the positive charges generated by the bending moment of the fixed beam 33. The generated positive charges flow through the outer ring electrode 44 and are finally led out through the lead-out electrode 45. By detecting the amount of positive charges generated on the lead-out electrode 45, the performance of the vibration sensor can be detected.

[0041] It should be understood that the orientation or positional relationship indicated by the terms "central", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0042] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0043] In the present invention, unless otherwise clearly defined and limited, terms such as "mounted", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and may be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0045] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered by the protection scope of the present invention.

Claims

1. A MEMS chip based on a uniaxial vibration sensor, comprising a substrate (1), the substrate (1) having opposite front and back surfaces, a piezoelectric layer provided on the front surface, the piezoelectric layer including a bottom electrode (2), a piezoelectric thin film (3), and a top electrode (4) stacked in sequence, a back cavity provided on the back surface, the structure of the chip within the longitudinal projection area corresponding to the back cavity being a diaphragm, the part opposite to the diaphragm being the diaphragm area, and the part not opposite to the diaphragm being the non - diaphragm area; Characterized in that, The piezoelectric thin film (3) includes a piezoelectric thin film main body (34) located in the non - diaphragm area and a central block (31), a plurality of cantilever beams (32), and a plurality of fixed beams (33) located in the diaphragm area; The central block (31) is located at the center of the diaphragm area, one end of the fixed beam (33) is connected to the central block (31), the other end is connected to the piezoelectric thin film main body (34), the cantilever beam (32) is located between two adjacent fixed beams (33) and forms a deformation gap with the fixed beams (33), one end of the cantilever beam (32) is connected to the central block (31), and the other end of the cantilever beam (32) is suspended; The top electrode (4) includes a central electrode (41), a plurality of floating electrodes (42) provided outside the central electrode (41) and connected to the central electrode (41), an outer ring electrode (44), a plurality of fixed electrodes (43) provided inside the outer ring electrode (44) and connected to the outer ring electrode (44), and an extraction electrode (45) provided outside the outer ring electrode (44) and connected to the outer ring electrode (44); The extraction electrode (45) is located in the non - diaphragm area, and the fixed electrode (43) is electrically connected to the central electrode (41); The central electrode (41) is provided on the central block (31), the floating electrode (42) is opposite to the part of the cantilever beam (32) close to the central block (31), the fixed electrode (43) is connected to the part of the fixed beam (33) far from the central block (31), and the outer ring electrode (44) is connected to the piezoelectric thin film main body (34); Wherein, the floating electrode (42) is used to collect positive charges on the cantilever beam (32), the fixed electrode (43) is used to collect positive charges on the fixed beam (33), and the positive charges collected by the floating electrode (42) and the fixed electrode (43) are fed back outwards through the outer ring electrode (44) and the extraction electrode (45); The cross - sectional area of the floating electrode (42) is smaller than the cross - sectional area of the cantilever beam (32), and the cross - sectional area of the fixed electrode (43) is smaller than the cross - sectional area of the fixed beam (33).

2. The MEMS chip based on a uniaxial vibration sensor according to claim 1, wherein The substrate (1) is an SOI substrate, including a bottom silicon (11), a buried oxide layer (12), and a top silicon (13) stacked in sequence.

3. The MEMS chip based on a uniaxial vibration sensor according to claim 2, wherein The structure of the bottom electrode (2) within the diaphragm area corresponds to that of the piezoelectric thin film (3).

4. The MEMS chip based on a uniaxial vibration sensor according to claim 3, characterized in that, The structure of the top silicon (13) within the diaphragm area corresponds to that of the bottom electrode (2).

5. The MEMS chip based on a uniaxial vibration sensor according to claim 4, characterized in that, The central block is of a cylindrical structure, and the axis line of the central block (31) coincides with the center line of the diaphragm region.

6. The MEMS chip based on a uniaxial vibration sensor according to claim 5, wherein The multiple cantilever beams (32) are arranged in a circular array along the central block (31).

7. The MEMS chip based on a uniaxial vibration sensor according to claim 6, characterized in that, The multiple fixing beams (33) are arranged in a circular array along the central block (31).

8. The MEMS chip based on a uniaxial vibration sensor according to claim 7, characterized in that, The number of the cantilever beams (32) is the same as that of the fixing beams (33), and they are arranged in a cross pattern.

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