A tunable MEMS structure based on piezoelectric stacks

Abstract

This invention discloses a tunable MEMS structure based on a piezoelectric stack, comprising a substrate having a front side and a back side. A piezoelectric layer is grown on the front side of the substrate, and a back cavity is formed on the back side of the substrate to provide vibration space for a diaphragm. A first height plate is provided on the front side of the substrate, forming a first dielectric cavity between the first height plate, the substrate, and the piezoelectric layer. A second height plate is provided on the back side of the substrate, forming a second dielectric cavity between the second height plate and the substrate. The first and second dielectric cavities together serve as a tuning cavity to construct a Helmholtz resonant cavity for the back cavity. A first through-hole communicating with the first dielectric cavity is formed on the sidewall of the first height plate, and a second through-hole communicating with the second dielectric cavity is formed on the sidewall of the second height plate. This invention enhances the MEMS structure effect through the dielectric cavities of the two height plates while simultaneously constructing a Helmholtz resonant cavity together with the back cavity. The resonant frequency of the diaphragm is adjusted by using a packaging process instead of a wafer-level etching process, enabling efficient energy coupling.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a tunable MEMS structure based on piezoelectric stacks. Background Technology

[0002] Micro-Electro-Mechanical Systems (MEMS), also known as micro-electromechanical systems, microsystems, or micromachines, refer to high-tech devices with dimensions of a few millimeters or even smaller. The internal structure of a MEMS is typically on the micrometer or even nanometer scale, making it an independent intelligent system. MEMS are developed based on microelectronics technology (semiconductor manufacturing technology) and integrate technologies such as photolithography, etching, thin film processing, LIGA, silicon micromachining, non-silicon micromachining, and precision machining to create high-tech electromechanical devices. MEMS are miniature devices or systems that integrate microsensors, microactuators, micromechanical structures, micropower supplies, signal processing and control circuits, high-performance integrated electronic devices, interfaces, and communication. MEMS is a revolutionary new technology widely used in high-tech industries and is a key technology related to national scientific and technological development, economic prosperity, and national defense security.

[0003] In existing technologies, the vibration frequency of MEMS chips produced through standardized wafer-level processes is fixed. Adjusting the frequency requires redefining process standards or rework, which is cumbersome and increases the risk of fragmentation.

[0004] In summary, this application proposes a tunable MEMS structure based on piezoelectric stacks to solve the aforementioned problems. Summary of the Invention

[0005] To address the technical problems existing in the background art, this invention proposes a tunable MEMS structure based on piezoelectric stacks.

[0006] The present invention proposes a tunable MEMS structure based on piezoelectric stack, including a substrate having a front side and a back side. A piezoelectric layer is grown on the front side of the substrate, and a back cavity is formed on the back side of the substrate to provide a vibration space for the diaphragm. Unlike the prior art, a first height plate is sealed and connected to the front side of the substrate, and a first dielectric cavity is formed between the first height plate, the substrate, and the piezoelectric layer.

[0007] The substrate is back-sealed with a second height plate, and a second groove is formed on the second height plate. The second groove communicates with the back cavity. A second dielectric cavity is formed between the second height plate and the substrate. The first dielectric cavity and the second dielectric cavity together serve as a tuning cavity to construct the Helmholtz resonant cavity of the back cavity.

[0008] The first height plate has a first through hole on its side wall that communicates with the first medium cavity, and the second height plate has a second through hole on its side that communicates with the second medium cavity.

[0009] This invention enhances the MEMS structure effect by forming a dielectric cavity (including a first dielectric cavity and a second dielectric cavity) with the substrate using two height plates (a first height plate and a second height plate). At the same time, it constructs a Helmholtz resonant cavity together with the back cavity. The resonant frequency of the diaphragm is adjusted by using a packaging process instead of a wafer-level etching process, enabling efficient energy coupling.

[0010] As a further optimization of the present invention, the substrate is an SOI substrate, comprising a bottom silicon layer, a buried oxide layer and a top silicon layer stacked sequentially, and the back cavity is formed by etching through the bottom silicon layer.

[0011] As a further optimization of the present invention, the piezoelectric layer includes a bottom electrode, a piezoelectric thin film, and a top electrode stacked sequentially; preferably, the piezoelectric thin film is a PZT piezoelectric thin film.

[0012] As a further optimization of the present invention, multiple first through holes are provided, and the multiple first through holes are distributed in a ring array on the side wall of the first height plate.

[0013] As a further optimization of the present invention, a third through hole communicating with the first medium cavity is provided on the first height plate, and the third through hole is opposite to the first through hole.

[0014] As a further optimization of the present invention, multiple third through holes are provided, and the multiple third through holes are distributed in a ring array on the first height plate.

[0015] As a further optimization of the present invention, multiple second through holes are provided, and the multiple second through holes are distributed in a ring array on the side wall of the second height plate.

[0016] As a further optimization of the present invention, the second height plate has a fourth through hole on its side that communicates with the second medium cavity, and the fourth through hole is opposite to the second through hole.

[0017] As a further optimization of the present invention, the second through hole corresponds one-to-one with the first through hole, and the axis of the corresponding first through hole and the axis of the second through hole are in the same vertical plane.

[0018] As a further optimization of the present invention, the cross-sectional area of ​​the second groove is larger than the cross-sectional area of ​​the back cavity, and the back cavity is opposite to the second groove, that is, the inner wall of the second groove is opposite to the back side of the substrate.

[0019] As a further optimization of the present invention, the piezoelectric layer is opposite to the back cavity, and the outer diameter or width of the piezoelectric layer is smaller than the outer diameter or width of the back cavity.

[0020] As a further optimization of the present invention, the first through hole is tapered, and the diameter of the first through hole gradually decreases from the end closer to the first medium cavity to the end farther away from the first medium cavity; and / or

[0021] The second through hole is a tapered hole, and the diameter of the second through hole gradually decreases from the end closer to the second medium cavity to the end farther away from the second medium cavity.

[0022] In this invention, the proposed tunable MEMS structure based on piezoelectric stacks enhances the MEMS structure effect through the dielectric cavity formed by two height plates and the substrate, while jointly constructing a Helmholtz resonant cavity with the back cavity. The resonant frequency of the diaphragm is adjusted by using packaging technology instead of wafer-level etching technology, enabling efficient energy coupling.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0025] Figure 2 This is a schematic diagram of a preferred structure according to Embodiment 1 of the present invention;

[0026] Figure 3 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0027] Figure 4 This is a schematic diagram of the structure of Embodiment 3 of the present invention;

[0028] Figure 5 This is a schematic diagram of the structure of Embodiment 4 of the present invention;

[0029] Figure 6 This is a schematic diagram of the structure of Embodiment 5 of the present invention;

[0030] In the figure: 1. Substrate; 11. Bottom silicon; 12. Buried oxide layer; 13. Top silicon; 2. First height plate; 21. First via; 22. Third via; 3. Piezoelectric layer; 4. Second height plate; 41. Second via; 42. Fourth via; 5. First dielectric cavity; 6. Second dielectric cavity. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] Example 1

[0033] like Figure 1 The tunable MEMS structure based on piezoelectric stack shown includes a substrate 1, which has a front side and a back side. A piezoelectric layer 3 is grown on the front side of the substrate 1. The piezoelectric layer 3 includes a bottom electrode, a piezoelectric thin film and a top electrode stacked sequentially. Preferably, the piezoelectric thin film is a PZT piezoelectric thin film.

[0034] The back side of the substrate 1 has a back cavity that provides a vibration space for the diaphragm. Optionally, the substrate 1 is an SOI substrate 1, which includes a bottom silicon 11, a buried oxide layer 12 and a top silicon 13 stacked in sequence, and the back cavity is formed by etching through the bottom silicon 11.

[0035] The front side of the substrate 1 is sealed with a first height plate 2. The first height plate 2 can be connected to the substrate 1 by adhesive. A first dielectric cavity 5 is formed between the first height plate 2, the substrate 1, and the piezoelectric layer 3. Specifically, a first groove is opened on the side of the first height plate 2 opposite to the substrate 1. The bottom surface of the first height plate 2 is sealed with the top surface of the substrate 1 to form the first dielectric cavity 5. The size of the piezoelectric layer 3 is smaller than the size of the first groove on the first height plate 2.

[0036] The back of the substrate 1 is sealed with a second height plate 4. The second height plate 4 can be sealed to the substrate 1 by adhesive. The second height plate 4 has a second groove that communicates with the back cavity. A second dielectric cavity 6 is formed between the second height plate 4 and the substrate 1. The first dielectric cavity 5 and the second dielectric cavity 6 together serve as a tuning cavity to construct the Helmholtz resonant cavity of the back cavity.

[0037] The side wall of the first height plate 2 has a first through hole 21 communicating with the first medium cavity 5, and the side of the second height plate 4 has a second through hole 41 communicating with the second medium cavity 6; preferably, the second through hole 41 corresponds one-to-one with the first through hole 21, and the axis of the corresponding first through hole 21 and the axis of the second through hole 41 are in the same vertical plane.

[0038] like Figure 2 As shown, preferably, multiple first through holes 21 are provided, and the multiple first through holes 21 are distributed in a ring array on the side wall of the first height plate 2; preferably, multiple second through holes 41 are provided, and the multiple second through holes 41 are distributed in a ring array on the side wall of the second height plate 4.

[0039] To improve accuracy, preferably, the cross-sectional area of ​​the second groove on the second height plate 4 is larger than the cross-sectional area of ​​the back cavity, and the back cavity is opposite to the second groove, that is, the inner wall of the second groove is opposite to the back side of the substrate 1.

[0040] The piezoelectric layer 3 drives the diaphragm to vibrate back and forth due to the piezoelectric effect. When the diaphragm moves away from the first height plate 2, the medium enters the first medium cavity 5 through the first through hole 21. When the diaphragm moves closer to the first height plate 2, it compresses the medium inside the first medium cavity 5 and causes the medium to be discharged from the first through hole 21.

[0041] The piezoelectric layer 3 drives the diaphragm to vibrate back and forth due to the piezoelectric effect. When the diaphragm moves away from the second height plate 44, the medium enters the second medium cavity 6 through the second through hole 41. When the diaphragm moves closer to the second height plate 4, it compresses the medium inside the second medium cavity 6 and causes the medium to be discharged from the second through hole 41.

[0042] This invention enhances the MEMS structure effect by forming a dielectric cavity (including a first dielectric cavity 5 and a second dielectric cavity) with the substrate 1 using two height plates 2 (first height plate 2 and second height plate 4). At the same time, it constructs a Helmholtz resonant cavity together with the back cavity. The resonant frequency is changed by altering the number and position of the first via 21 and the second via 41. The resonant frequency of the diaphragm is adjusted by using a packaging process instead of a wafer-level etching process, enabling efficient energy coupling.

[0043] Example 2

[0044] like Figure 3 As shown, in this embodiment, based on the above embodiment, a third through hole 22 communicating with the first medium cavity 5 is opened on the first height plate 2, and the third through hole 22 is opposite to the first through hole 21; optionally, multiple third through holes 22 are provided, and the multiple third through holes 22 are distributed in a ring array on the first height plate 2.

[0045] Example 3

[0046] Please see Figure 4 Based on a preferred embodiment of Embodiment 1 or Embodiment 2, the tunable MEMS structure based on piezoelectric stack proposed in this embodiment has a fourth through hole 42 on the side of the second height plate 2 that communicates with the second dielectric cavity 6. The fourth through hole 42 is opposite to the second through hole 41. Optionally, multiple sets of fourth through holes 42 are provided, and the multiple sets of fourth through holes 42 are distributed in a ring on the second height plate 4.

[0047] Example 4

[0048] Please see Figure 5Based on a preferred embodiment of Embodiments 1, 2, and 3, the tunable MEMS structure based on piezoelectric stack proposed in this embodiment has a first through-hole 21 that is tapered, and the diameter of the first through-hole 21 gradually decreases from the end near the first dielectric cavity 5 to the end away from the first dielectric cavity 5; the second through-hole 41 is a tapered hole, and the diameter of the second through-hole 41 gradually decreases from the end near the second dielectric cavity 6 to the end away from the second dielectric cavity 6, so that the air pressure entering the first dielectric cavity 5 or the second dielectric cavity 6 decreases from high to low.

[0049] Example 5

[0050] Please see Figure 6 Based on a preferred embodiment of Embodiment 4, the tunable MEMS structure based on piezoelectric stack proposed in this embodiment has a third through-hole 22 that is tapered, and the diameter of the third through-hole 22 gradually increases from the end near the first dielectric cavity 5 to the end away from the first dielectric cavity 5; the fourth through-hole 42 is a tapered hole, and the diameter of the fourth through-hole 42 gradually increases from the end near the second dielectric cavity 6 to the end away from the second dielectric cavity 6, thereby ensuring the fluidity performance of the medium during diaphragm vibration and ensuring accuracy.

[0051] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0052] Furthermore, 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 number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0053] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between the components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0054] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A tunable MEMS structure based on a piezoelectric stack, comprising a substrate (1) having opposing front and back sides, wherein a piezoelectric layer (3) is grown on the front side of the substrate (1), and a back cavity is formed on the back side of the substrate (1) to provide a vibration space for a diaphragm, characterized in that, The front side of the substrate (1) is sealed with a first height plate (2), and a first dielectric cavity (5) is formed between the first height plate (2), the substrate (1), and the piezoelectric layer (3); The back of the substrate (1) is sealed with a second height plate (4), and a second groove is opened on the second height plate (4). The second groove communicates with the back cavity. A second dielectric cavity (6) is formed between the second height plate (4) and the substrate (1). The first dielectric cavity (5) and the second dielectric cavity (6) together serve as a tuning cavity to construct the Helmholtz resonant cavity of the back cavity. The first height plate (2) has a first through hole (21) communicating with the first medium cavity (5) on its side wall, and the second height plate (4) has a second through hole (41) communicating with the second medium cavity (6) on its side. The substrate (1) includes a bottom silicon (11), a buried oxide layer (12) and a top silicon (13) stacked sequentially, and the back cavity is formed through the bottom silicon (11); The first through hole (21) is provided in multiple ways, and the multiple first through holes (21) are distributed in a ring array on the side wall of the first height plate (2); The second through hole (41) is provided in multiple ways, and the multiple second through holes (41) are distributed in a ring array on the side wall of the second height plate (4); The piezoelectric layer (3) drives the diaphragm to vibrate back and forth due to the piezoelectric effect. When the diaphragm moves away from the first height plate (2), the medium enters the first medium cavity (5) through the first through hole (21). When the diaphragm moves closer to the first height plate (2), it compresses the medium inside the first medium cavity (5) and causes the medium to be discharged from the first through hole (21). The piezoelectric layer (3) drives the diaphragm to vibrate back and forth due to the piezoelectric effect. When the diaphragm moves away from the second height plate (4), the medium enters the second medium cavity (6) through the second through hole (41). When the diaphragm moves closer to the second height plate (4), it compresses the medium inside the second medium cavity (6) and causes the medium to be discharged from the second through hole (41). The dielectric cavity formed by the first height plate (2) and the second height plate (4) and the substrate (1) enhances the MEMS structure effect, while jointly constructing a Helmholtz resonant cavity with the back cavity. The resonant frequency is changed by altering the number and position of the first through hole (21) and the second through hole (41). The resonant frequency of the diaphragm is adjusted by replacing the wafer-level etching process with the packaging process.

2. The tunable MEMS structure based on piezoelectric stacks according to claim 1, characterized in that, The piezoelectric layer (3) includes a bottom electrode, a piezoelectric film and a top electrode stacked in sequence, wherein the piezoelectric film is a PZT piezoelectric film.

3. The tunable MEMS structure based on piezoelectric stacks according to any one of claims 1-2, characterized in that, The first height plate (2) has a third through hole (22) that communicates with the first medium cavity (5), and the third through hole (22) is opposite to the first through hole (21).

4. The tunable MEMS structure based on piezoelectric stacks according to claim 1, characterized in that, The second height plate (4) has a fourth through hole (42) on its side that communicates with the second medium cavity (6), and the fourth through hole (42) is opposite to the second through hole (41).

5. The tunable MEMS structure based on piezoelectric stacks according to claim 1, characterized in that, The inner wall of the second groove is opposite to the back side of the substrate (1).

6. The tunable MEMS structure based on piezoelectric stacks according to claim 1, characterized in that, The first through hole (21) is tapered, and the diameter of the first through hole (21) gradually decreases from the end closest to the first medium cavity (5) to the end furthest from the first medium cavity (5); and / or The second through hole (41) is a tapered hole, and the diameter of the second through hole (41) gradually decreases from the end near the second medium cavity (6) to the end away from the second medium cavity (6).

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