PMUT with performance enhanced through cantilever beam structure
Through the PMUT design of cantilever beam structure, the bandwidth and axial resolution of PMUT are enhanced, and the problems of narrow bandwidth and low resolution of traditional PMUT devices are solved, thereby realizing high-resolution imaging applications.
Patent Information
- Application Number
- CN202422113912.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2025-08-22
- Estimated Expiration
- 2034-08-30
AI Technical Summary
Traditional PMUT devices have narrow bandwidth and low axial resolution, which cannot meet the high resolution requirements of medical ultrasound imaging and fingerprint recognition imaging, limiting their applications in the field of imaging.
The PMUT design adopts the cantilever beam structure. Through the stress corners of the cantilever beam and the resonant beam of different lengths, the bandwidth and axial resolution of the device are enhanced, forming a polygon spliced top electrode and piezoelectric layer, and using the piezoelectric effect to convert mechanical vibration into electrical signals.
It improves the axial resolution of PMUT, supports harmonic imaging and resonant imaging, and meets the needs of high-resolution imaging.
Smart Images
Figure CN223249790U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of semiconductor processes, and particularly relates to a PMUT whose performance is enhanced by a cantilever beam structure. Background Art
[0002] Piezoelectric materials, as a new generation of smart materials, have attracted widespread attention due to their mechanical-to-electrical energy conversion capabilities. With the rapid development of MEMS (microelectromechanical systems) in recent years, MEMS sensor chips made from piezoelectric thin films have advantages such as miniaturization and low power consumption. PMUTs (piezoelectric ultrasonic transducers), as important ultrasonic devices, are widely used in fields such as ranging, imaging, and fingerprint recognition.
[0003] However, while PMUT research has been relatively successful in miniaturization, medical ultrasound imaging will require increasingly larger PMUT arrays to achieve higher clarity, and fingerprint recognition imaging will require more and more PMUT units to achieve higher resolution. Traditional PMUTs are single-frequency, narrowband devices. This narrow bandwidth results in low axial resolution and makes them unsuitable for harmonic or resonant imaging, severely limiting their application in imaging. Utility Model Content
[0004] In view of the problems mentioned in the background technology, the purpose of the present invention is to provide a PMUT with enhanced performance through a cantilever beam structure, so as to solve the problems mentioned in the background technology.
[0005] The above technical objectives of the present invention are achieved through the following technical solutions:
[0006] A PMUT with enhanced performance through a cantilever beam structure includes a substrate and a piezoelectric layer. The substrate has opposite front and back surfaces. The piezoelectric layer is located on the front surface of the substrate. The piezoelectric layer includes a bottom electrode, a piezoelectric film, and a top electrode stacked in sequence. The top electrode includes a polygon composed of at least three groups of cantilever beams. The cross-section of the cantilever beams is a polygon formed by splicing multiple groups of trapezoids. The joints of the trapezoids form stress corners that concentrate stress. The multiple groups of cantilever beams are thermally bonded into an annular whole through air. The middle of the top electrode is an equilateral center hole formed by splicing the multiple groups of cantilever beams. A splicing seam is formed between adjacent cantilever beams near one end of the center hole.
[0007] As a preferred technical solution, the gap of the splicing seam is less than 9um.
[0008] As a preferred technical solution, the lengths of any cantilever beams are different.
[0009] As a preferred technical solution, the piezoelectric film is formed on a side of the bottom electrode close to the top electrode, and the bottom electrode is formed on the front side of the substrate.
[0010] As a preferred technical solution, the substrate is an SOI substrate.
[0011] As a preferred technical solution, the substrate includes bottom silicon, buried oxide layer and top silicon stacked in sequence, the bottom end of the bottom electrode is arranged on the top silicon, and a vibration cavity is opened through the bottom silicon and the buried oxide layer.
[0012] As a preferred technical solution, the piezoelectric film, the bottom electrode and the top silicon are all penetrated by through seams corresponding to the positions of the splicing seams and having the same width, and multiple groups of through seams extend toward the center and are interconnected.
[0013] As a preferred technical solution, the cross section of the vibration cavity corresponds to the cross section of the top electrode in position and has the same shape.
[0014] As a preferred technical solution, the top electrode forms a PMUT diaphragm within the projection range on the piezoelectric film, the bottom electrode and the top silicon, and the cross-sectional shape of the PMUT diaphragm is the same as that of the top electrode.
[0015] Beneficial effects
[0016] After receiving the ultrasonic signal, the top electrode converts the mechanical vibration into an electrical signal, causing the piezoelectric layer to produce a piezoelectric effect. When mechanical vibration is applied, the stress corners of the cantilever beams concentrate stress on the PMUT diaphragm, resulting in improved performance compared to traditional straight beams, trapezoidal beams, and triangular beams. Each set of cantilever beams has a different length, forming resonant beams of varying lengths. These varying resonant beams provide a wide bandwidth, resulting in high axial resolution for the device and greater benefits for imaging applications, such as harmonic imaging or resonant imaging.
[0017] Additional aspects and advantages of the present invention will be given in part in the following description and will become apparent from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 This is an exploded diagram of the structure of a PMUT proposed in the present invention that enhances performance through a cantilever beam structure;
[0019] Figure 2 for Figure 1 Schematic diagram of the structure of the middle cantilever beam;
[0020] Figure 3 for Figure 1 Schematic diagram of the structure of the top electrode Figure 1 ;
[0021] Figure 4 for Figure 1 Schematic diagram of the structure of the top electrode Figure 2 ;
[0022] Figure 5 for Figure 1 Schematic diagram of the structure of the medium voltage layer;
[0023] Figure 6 for Figure 1 Schematic diagram of the structure of the middle and bottom electrodes;
[0024] Figure 7 for Figure 1 Schematic diagram of the structure of the top silicon;
[0025] Figure 8 for Figure 1 Schematic diagram of the structure of the buried oxygen layer;
[0026] Figure 9 for Figure 1 Schematic diagram of the structure of the midsole silicon.
[0027] Figure numerals: 1. top electrode; 11. cantilever beam; 12. stress corner; 13. joint seam; 14. center hole; 2. piezoelectric film; 3. bottom electrode; 4. top silicon; 5. buried oxide layer; 6. bottom silicon; 7. through seam; 8. vibration cavity. DETAILED DESCRIPTION
[0028] The following describes in detail embodiments of the present invention. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention, and should not be construed as limiting the present invention.
[0029] Example 1
[0030] refer to Figures 1 to 9 The PMUT described in this embodiment has a cantilever beam structure that enhances performance, and includes a substrate and a piezoelectric layer. The substrate has a front side and a back side relative to each other. The piezoelectric layer is located on the front side of the substrate. The piezoelectric layer includes a bottom electrode 3, a piezoelectric film 2, and a top electrode 1 stacked in sequence. The top electrode 1 includes a polygon consisting of at least three groups of cantilever beams 11. The cross-section of the cantilever beam 11 is a polygon formed by splicing multiple groups of trapezoids. The joints of the trapezoids form stress corners 12. The multiple groups of cantilever beams 11 are thermally bonded into an annular whole by air. The middle of the top electrode 1 is an equilateral center hole 14 formed by splicing multiple groups of cantilever beams 11. A splicing seam 13 is formed between adjacent cantilever beams 11 near one end of the center hole 14.
[0031] The gap of the joint seam 13 is less than 9 μm.
[0032] The lengths of the multiple groups of cantilever beams 11 are different.
[0033] The piezoelectric layer 2 is formed on the side of the bottom electrode 3 close to the top electrode 1, and the bottom electrode 3 is formed on the front side of the substrate. The piezoelectric layer 2 and the bottom electrode 3 are both penetrated by a through seam 7 corresponding to the position of the splicing seam 13 and the same width as the splicing seam 13. Multiple groups of through seams 7 extend toward the center and are interconnected.
[0034] The substrate is an SOI substrate, which includes a bottom silicon 6, a buried oxide layer 5 and a top silicon 4 stacked in sequence. The bottom electrode 3 is arranged on the front of the top silicon 4. The top silicon 4 is provided with a through seam 7 that is the same as the corresponding one on the piezoelectric layer 2. The top electrode 1 constitutes a PMUT diaphragm within the projection range on the piezoelectric layer 2, the bottom electrode 3 and the top silicon 4. A vibration cavity 8 for the PMUT diaphragm to vibrate is provided through the bottom silicon 6 and the buried oxide layer 5.
[0035] The cross section of the vibration cavity 8 corresponds in position to the cross section of the top electrode 1 and has the same shape.
[0036] After receiving the ultrasonic signal, the top electrode 1 converts the mechanical vibration into an electrical signal, causing the piezoelectric layer to produce a piezoelectric effect. When mechanical vibration is applied, the stress corners 12 of the cantilever beams 11 concentrate stress on the PMUT diaphragm, resulting in improved performance compared to traditional straight beams, trapezoidal beams, and triangular beams. Each set of cantilever beams 11 has a different length, forming resonant beams of varying lengths. These varying resonant beams provide a wide bandwidth, resulting in high axial resolution for the device and greater benefits for imaging applications, such as harmonic imaging or resonant imaging.
[0037] 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 to 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 device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.
[0038] 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 the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this utility model, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.
[0039] In this utility model, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. For those skilled in the art, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.
[0040] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.
[0041] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.
Claims
1. A PMUT with enhanced performance through a cantilever beam structure, comprising a substrate and a piezoelectric layer, characterized in that: The substrate has a front side and a back side facing each other, and the piezoelectric layer is located on the front side of the substrate. The piezoelectric layer includes a bottom electrode (3), a piezoelectric film (2) and a top electrode (1) stacked in sequence. The top electrode (1) includes a polygon composed of at least three groups of cantilever beams (11). The cross section of the cantilever beam (11) is a polygon formed by splicing multiple groups of trapezoids. The joints of the trapezoids form stress corners (12) for concentrated stress. The multiple groups of cantilever beams (11) are bonded together into a ring-shaped whole by air heat bonding. The middle of the top electrode (1) is an equilateral center hole (14) formed by splicing multiple groups of cantilever beams (11). A splicing seam (13) is formed between adjacent cantilever beams (11) near one end of the center hole (14).
2. The PMUT with enhanced performance through a cantilever beam structure according to claim 1, characterized in that: The gap of the splicing seam (13) is less than 9 μm.
3. The PMUT with enhanced performance through a cantilever beam structure according to claim 1, characterized in that: The lengths of any cantilever beam (11) are different.
4. The PMUT with enhanced performance through a cantilever beam structure according to claim 1, wherein: The piezoelectric film (2) is formed on a side of the bottom electrode (3) close to the top electrode (1), and the bottom electrode (3) is formed on the front side of the substrate.
5. The PMUT with enhanced performance through a cantilever beam structure according to claim 1, wherein: The substrate is an SOI substrate.
6. The PMUT with enhanced performance through a cantilever beam structure according to claim 5, characterized in that: The substrate comprises bottom silicon (6), a buried oxide layer (5) and a top silicon (4) which are stacked in sequence. The bottom end of the bottom electrode (3) is arranged on the top silicon (4). A vibration cavity (8) is provided through both the bottom silicon (6) and the buried oxide layer (5).
7. The PMUT with enhanced performance through a cantilever beam structure according to claim 6, characterized in that: The piezoelectric film (2), the bottom electrode (3) and the top silicon (4) are all penetrated by through seams (7) corresponding to the positions of the splicing seams (13) and having the same width as the splicing seams (13), and multiple groups of through seams (7) extend toward the center and are interconnected.
8. The PMUT with enhanced performance through a cantilever beam structure according to claim 6, characterized in that: The cross section of the vibration cavity (8) corresponds in position to the cross section of the top electrode (1) and has the same shape.
9. The PMUT with enhanced performance through a cantilever beam structure according to claim 6, characterized in that: The top electrode (1) forms a PMUT diaphragm within the projection range on the piezoelectric film (2), the bottom electrode (3) and the top silicon (4), and the cross-sectional shape of the PMUT diaphragm is the same as that of the top electrode (1).