MEMS chip based on single-axis vibration sensor

Abstract

The invention discloses an MEMS chip based on a uniaxial vibration sensor, and relates to the technical field of semiconductor technology, the MEMS chip comprises a substrate, the substrate is provided with a front surface and a back surface which are opposite, the front surface is provided with a piezoelectric layer, the piezoelectric layer comprises a bottom electrode, a piezoelectric film and a top electrode which are stacked in sequence, the structure, corresponding to the back cavity longitudinal projection area, of the chip is a vibrating diaphragm, the piezoelectric layer of the back cavity longitudinal projection area is the vibrating diaphragm, the piezoelectric film comprises a piezoelectric film body located in a non-vibrating-diaphragm area, a center block, a plurality of cantilever beams and a plurality of fixed beams, the center block is located in the center of the vibrating diaphragm area, and the cantilever beams are located in the center of the vibrating diaphragm area. The two ends of the fixed beam are connected with the center block and the piezoelectric film body respectively, one end of the cantilever beam is connected with the center block, and the cantilever beam amplifies the borne force. According to the invention, the sensitivity is improved through the effect of the amplification force of the cantilever beam, and the stability of the chip is improved through 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 smart materials, piezoelectric materials have attracted widespread attention due to their mechanical-electrical energy conversion performance. With the rapid development of micro-electromechanical systems (MEMS) in recent years, MEMS sensor chips made of piezoelectric films have the advantages of miniaturization and low power consumption. As an important inertial device, micromechanical accelerometers are widely used in various fields such as inertial navigation, acceleration measurement, medical diagnosis, health monitoring and disaster warning.

[0003] The classic structures of piezoelectric MEMS vibration sensors are mainly cross-beam type, annular mass block, and single cantilever beam. However, the typical cross-beam type accelerometer is a three-axis accelerometer. In actual use, it is necessary to decouple the outputs in each direction. The annular mass block type accelerometer has too small sensitivity output in the single axis (Z) direction due to the excessive film stiffness. Although the single cantilever beam accelerometer has a simple structure, it needs to be connected in series and parallel to meet the high sensitivity requirements. Summary of the invention

[0004] In order to solve the technical problems existing in the background technology, the present invention proposes a MEMS chip based on a uniaxial vibration sensor.

[0005] A MEMS chip based on a uniaxial vibration sensor proposed in the present invention comprises a substrate, wherein the substrate has a front side and a back side opposite to each other, a piezoelectric layer is arranged on the front side, the piezoelectric layer comprises a bottom electrode, a piezoelectric film and a top electrode stacked in sequence, a back cavity is opened on the back side, a structure within the longitudinal projection area of ​​the chip corresponding to the back cavity is a diaphragm, a part opposite to the diaphragm is a diaphragm area, and a part not opposite to the diaphragm is a non-diaphragm area;

[0006] The piezoelectric film comprises a piezoelectric film body, a central block, a plurality of cantilever beams and a plurality of fixed beams, the piezoelectric film body is located in the non-diaphragm area of ​​the diaphragm, the central block is located in the diaphragm area, and the plurality of cantilever beams and the plurality of fixed beams are located on the periphery of the central block;

[0007] The central block is located at the center of the diaphragm area, 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 in the air; the cantilever beam amplifies the force it receives, and the sensitivity is improved by the cantilever beam amplifying the force, and the stability of the chip is improved by the fixed beam, and 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 to the outside.

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

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

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

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

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

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

[0014] Preferably, the cantilever beams and the fixed beams are of the same number and are arranged crosswise.

[0015] Preferably, the top electrode comprises a central electrode, a plurality of suspended electrodes arranged outside the central electrode and connected to the central electrode, an outer ring electrode, a plurality of 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 area, and the fixed electrode is electrically connected to the central electrode;

[0017] The central electrode is arranged on the central block, the floating electrode is opposite to the portion of the cantilever beam close to the central block, the fixed electrode is connected to the portion of the fixed beam away from the central block, and the outer ring electrode is connected to the piezoelectric film body;

[0018] The floating electrode is used to collect positive charges on the cantilever beam, and the fixed electrode is used to collect positive charges on the fixed beam. The positive charges collected by the floating electrode and the fixed electrode are fed back to the outside through the outer ring electrode and the lead-out electrode.

[0019] Preferably, the cross-sectional area of ​​the floating electrode is smaller than the cross-sectional area of ​​the cantilever beam, and the cross-sectional area of ​​the fixed electrode is smaller than the cross-sectional area 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 by fixing the beam and the high symmetry of the chip itself, so that the lateral sensitivity of the final vibration sensor is negligible, and there is no need to decouple the received acceleration signal; at the same time, the cantilever beam in the MEMS chip proposed in the embodiment of the present invention uses the center block as an anchor point and acts 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 and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the structure of a MEMS chip based on a uniaxial vibration sensor proposed in an embodiment of the present invention;

[0023] Figure 2 for Figure 1 Exploded diagram of the structure;

[0024] Figure 3 for Figure 1 Front view of

[0025] Figure 4 for Figure 1 A top view of

[0026] Figure 5 for Figure 1 Bottom view of

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

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

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

[0030] Fig. 9 is a schematic diagram of a 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 film; 31. center block; 32. cantilever beam; 33. fixed beam; 34. piezoelectric film body; 4. top electrode; 41. center electrode; 42. suspended electrode; 43. fixed electrode; 44. outer ring electrode; 45. lead-out electrode. DETAILED DESCRIPTION

[0032] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

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

[0034] A cylindrical groove is provided on the back 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 is a vibration space released by the diaphragm, the part of the chip opposite to the diaphragm is a diaphragm area, and the part of the chip not opposite to the diaphragm is a 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 is provided through the bottom silicon 11 and the buried oxide layer 12;

[0035] The piezoelectric layer includes a bottom electrode 2, a piezoelectric film 3 and a top electrode 4 which are sequentially stacked on the front side of the substrate.

[0036] like Figure 7 As shown, the structure of the piezoelectric film 3 is made by etching, and the piezoelectric film includes a piezoelectric film body 34 located in the non-diaphragm area and a central block 31 located in the diaphragm area, a plurality of cantilever beams 32 and a plurality of fixed beams 33, the central block 31 is located in the center of the diaphragm area and is a cylindrical structure, the axis 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 of the central block 31 coincides with the axis of the diaphragm, and the two ends of the fixed beam 33 are respectively connected to the central block 31 and the piezoelectric film body 34, that is, the fixed beam 33 The fixed beam 33 connects the central block 31 and the piezoelectric film 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 film body 34. Optionally, the fixed beams 33 and the cantilever beams 32 are the same in number and arranged crosswise, and a plurality of cantilever beams 32 are arranged in a circular array along the central block 31, and a 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 beams 32 and the fixed beams 33.

[0037] The structure of the bottom electrode 2 located in the diaphragm region corresponds to the piezoelectric film 3;

[0038] The structure of the top of the top silicon 13 of the substrate 1 located in the diaphragm region is the same as and corresponds to the bottom electrode 2 (eg Fig. 9shown).

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

[0040] like Figure 6As shown, the top electrode 4 includes a central electrode 41, a plurality of suspended electrodes 42, a plurality of fixed electrodes 43, an outer ring electrode 44 and an extraction electrode 45. The central electrode 41 is arranged on the surface of the central block 31, and the central electrode 41 is a cylindrical structure, and the axis of the central electrode 41 coincides with the axis of the central block 31. The number of suspended electrodes 42 is the same as the number of cantilever beams 32, and each cantilever beam 32 is provided with a suspended electrode 42, and the plurality of suspended electrodes 42 are arranged in a ring array along the central electrode 41, and the cross-sectional area of ​​the suspended electrode 42 is smaller than the cross-sectional area of ​​the cantilever beam 32, and the suspended electrode 42 is located on the cantilever beam 32 near the central block 31, and one end of the suspended electrode 42 near 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. Each fixed beam 33 is provided with a fixed electrode 43, and multiple fixed electrodes 43 are arranged in a ring 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 on the fixed beam 33 away from the central block 31. The fixed electrodes 43a and 43b that are centrally symmetrical among the multiple fixed electrodes 43 are both electrically connected to the central electrode 41. The outer ring electrode 44 is an annular structure, the axis of the outer ring electrode 44 coincides with the center line of the diaphragm area, the inner diameter of the outer ring electrode 44 is larger than the diameter of the diaphragm area, and each fixed electrode 43 is electrically connected to the outer ring electrode 44. The lead-out electrode 45 is located in the non-diaphragm area and in the area outside the longitudinal projection area of ​​the outer ring electrode 44, and 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., longitudinal direction), according to solid mechanics, the bending moments received by the cantilever beam 32 and the fixed beam 33 are positive and negative, which are manifested on the piezoelectric vibration sensor to generate positive and negative charges. The setting of the floating electrode 42 and the fixed electrode 43 enables the floating electrode 42 to collect the positive charge generated by the bending moment of the cantilever beam 32, and the fixed electrode 43 to collect the positive charge generated by the bending moment of the fixed beam 33. The generated positive charge flows through the outer ring electrode 44 and is finally led out through the lead-out electrode 45. By detecting the amount of positive charge generated on the lead-out electrode 45, the performance of the vibration sensor can be detected.

[0041] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0042] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0043] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, 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 specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0045] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which 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 a front side and a back side opposite to each other, the front side being provided with a piezoelectric layer, the piezoelectric layer comprising a bottom electrode (2), a piezoelectric film (3) and a top electrode (4) stacked in sequence, the back side being provided with a back cavity, the structure of the chip within the longitudinal projection area of ​​the back cavity being a diaphragm, the portion opposite to the diaphragm being a diaphragm area, and the portion not opposite to the diaphragm being a non-diaphragm area; It is characterized in that The piezoelectric film (3) comprises a piezoelectric film body (34) located in a non-diaphragm region, a central block (31) located in a diaphragm region, a plurality of cantilever beams (32) and a plurality of fixed beams (33); 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), and the other end is connected to the piezoelectric film 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.

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

3. The MEMS chip based on a uniaxial vibration sensor according to claim 2, characterized in that: The structure in which the bottom electrode (2) is located in the diaphragm region corresponds to the piezoelectric 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) located in the diaphragm area corresponds to 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 a cylindrical structure, and the axis of the central block (31) coincides with the center line of the diaphragm area.

6. The MEMS chip based on a uniaxial vibration sensor according to claim 5, characterized in that: The plurality of 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 plurality of fixed 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 cantilever beams (32) and the fixed beams (33) are the same in number and are cross-arranged.

9. The MEMS chip based on a uniaxial vibration sensor according to any one of claims 1 to 8, characterized in that: The top electrode (4) comprises a central electrode (41), a plurality of suspended electrodes (42) arranged outside the central electrode (41) and connected to the central electrode (41), an outer ring electrode (44), a plurality of fixed electrodes (43) arranged inside the outer ring electrode (44) and connected to the outer ring electrode (44), and an extraction electrode (45) arranged 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 arranged on the central block (31), the floating electrode (42) is opposite to the portion of the cantilever beam (32) close to the central block (31), the fixed electrode (43) is connected to the portion of the fixed beam (33) away from the central block (31), and the outer ring electrode (44) is connected to the piezoelectric film body (34); The floating electrode (42) is used to collect positive charges on the cantilever beam (32), and the fixed electrode (43) is used to collect positive charges on the fixed beam (33). The positive charges collected by the floating electrode (42) and the fixed electrode (43) are fed back to the outside through the outer ring electrode (44) and the extraction electrode (45).

10. The MEMS chip based on a uniaxial vibration sensor according to claim 9, characterized in that: 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).

Images