MEMS acoustic sensor chip

Abstract

The MEMS acoustic sensor chip is characterized in that the MEMS acoustic sensor chip comprises a silicon substrate layer (1), a silicon oxide structure layer (2) and a silicon structure layer (3), cavities (7) are formed in the silicon substrate layer (1) and the silicon oxide structure layer (3), through holes (8) communicated with the cavities (7) are formed in the bottom of the silicon substrate layer (1), and a bottom electrode layer (4), a piezoelectric layer (5) and a top electrode layer (6) are sequentially arranged on the silicon structure layer (3). A hole (5a) is provided in the piezoelectric layer (5). The piezoelectric film type MEMS acoustic sensor is simple in structure and convenient to use, and the problem that the piezoelectric film type MEMS acoustic sensor loses efficacy and even is damaged due to inward sinking of the film caused by high hydrostatic pressure is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS chips and acoustic sensor packaging, and in particular to a MEMS acoustic sensor chip. Background Art

[0002] The ocean is a crucial base for the human ecosystem and a vital space for national defense and military development. Underwater acoustic sensors, the "ears" of active and passive sonar, are essential devices for ocean exploration.

[0003] Traditional piezoelectric ceramic underwater acoustic sensors are large in size and difficult to manufacture uniformly, making them unsuitable for arraying. Towed array cables made with these sensors are large in diameter, heavy, and difficult to tow, making them incapable of effectively detecting underwater radiated noise from miniature underwater detection platforms such as small unmanned underwater vehicles. MEMS acoustic sensors offer advantages such as small size, low cost, low power consumption, and high manufacturing consistency. Among them, piezoelectric thin-film MEMS (Micro-Electro-Mechanical Systems) acoustic sensors offer advantages such as simple structure, high sensitivity, low noise floor, low power consumption, and strong environmental adaptability.

[0004] However, when applied to deep-sea acoustic detection, high hydrostatic pressure can lead to uneven pressure between the outer and back chambers of the piezoelectric film, causing the film to sag inward, leading to failure or even damage of the piezoelectric film MEMS acoustic sensor. Chinese patent CN118836960 A discloses a method for packaging a MEMS deep-sea hydrophone, which improves its hydrostatic pressure resistance and operating depth. However, this method, which achieves pressure balance by bidirectionally filling the front and back sides of the diaphragm with oil, significantly reduces the sensitivity of the hydrophone.

[0005] Therefore, it is urgent to design a MEMS acoustic sensor chip that can ensure pressure balance on both sides of the piezoelectric film while minimizing the reduction in sensitivity. Summary of the Invention

[0006] The present invention aims to overcome the deficiencies in the prior art and provides a MEMS acoustic sensor chip.

[0007] This application provides the following technical solutions: A MEMS acoustic sensor chip, characterized in that it includes: a silicon substrate layer, a silicon oxide structural layer, and a silicon structural layer distributed sequentially from bottom to top; a cavity is provided on the silicon substrate layer and the silicon oxide structural layer below the silicon structural layer; a through hole connected to the cavity is provided at the bottom of the silicon substrate layer; a bottom electrode layer, a piezoelectric layer, and a top electrode layer with a smaller area are distributed sequentially from bottom to top on the silicon structural layer; a hole is provided in the piezoelectric layer on one side of the top electrode layer to expose the bottom electrode layer.

[0008] On the basis of the above technical solutions, the following further technical solutions can be provided: The hole extends into the bottom electrode layer to a certain depth.

[0009] Advantages of the invention: The present invention has a simple structure and is easy to use. It is based on a chip that uses a back cavity through-hole to balance the pressure on both sides of the piezoelectric film MEMS acoustic sensor when facing high hydrostatic pressure applications, thereby avoiding the problem of uneven pressure between the outer side of the piezoelectric film and the back cavity due to high hydrostatic pressure, causing the film to sag inward, resulting in failure or even damage to the piezoelectric film MEMS acoustic sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is a schematic diagram of the present invention for achieving upper and lower pressure balance of the membrane for underwater acoustic detection. DETAILED DESCRIPTION

[0011] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0012] It should be noted that, in the description of the present invention, the terms "front", "back", "left", "right", "up", "down", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present invention.

[0013] like Figure 1 and 2 As shown, a MEMS acoustic sensor chip comprises, from bottom to top, a silicon substrate layer 1, a silicon oxide structure layer 2, and a silicon structure layer 3. A cavity 7 is provided on the silicon substrate layer 1 and the silicon oxide structure layer 2 below the silicon structure layer 3. A through-hole 8 communicating with the cavity 7 is provided at the bottom of the silicon substrate layer 1. A bottom electrode layer 4 and a piezoelectric layer 5 are provided on the silicon structure layer 3 from bottom to top. A smaller top electrode layer 6 is deposited or sputtered on the upper surface of the piezoelectric layer 5. This allows for electrical connection between the top electrode and an external interface.

[0014] A hole 5a is etched into the piezoelectric layer 5 on one side of the top electrode layer 6. The hole 5a extends a certain depth into the bottom electrode layer 4, exposing the bottom electrode layer 4. This allows electrical connection to an external interface via wires or welding. The piezoelectric layer 5, bottom electrode layer 4, and silicon structure layer 3, arranged in order from top to bottom, form a piezoelectric thin film structure 9.

[0015] The piezoelectric thin film MEMS acoustic sensor is fabricated based on Cavity Silicon-On-Insulator (C-SOI). Therefore, the back cavity 7 is pre-existing. The through hole 8 connecting the back cavity 7 is obtained by etching the back of the wafer. This is used to maintain the upper and lower pressure balance of the piezoelectric thin film MEMS acoustic sensor film during packaging and filling, preventing the piezoelectric film from sinking inward or failing when high hydrostatic pressure is applied.

[0016] In actual applications for underwater acoustic detection, the packaging filling liquid 10 generates a pressure difference with the back cavity 7, which generates pressure on the upper surface of the piezoelectric film 9. At this time, the filling liquid 10 enters the pipeline connected to the through hole 8. When it reaches a certain position, the internal pressure of the back cavity 7 and the pressure of the filling liquid 10 on the piezoelectric film structure 9 are balanced. The position where the filling liquid 10 enters the pipeline connected to the through hole 8 varies with the size of the external hydrostatic pressure on the underwater acoustic sensor.

Claims

1. A MEMS acoustic sensor chip, characterized in that: The invention comprises a silicon substrate layer (1), a silicon oxide structural layer (2) and a silicon structural layer (3) distributed in sequence from bottom to top; a cavity (7) is provided on the silicon substrate layer (1) and the silicon oxide structural layer (2) below the silicon structural layer (3); a through hole (8) connected to the cavity (7) is provided at the bottom of the silicon substrate layer (1); a bottom electrode layer (4), a piezoelectric layer (5) and a top electrode layer (6) with a smaller area are distributed in sequence from bottom to top on the silicon structural layer (3); and a hole (5a) is provided on the piezoelectric layer (5) on one side of the top electrode layer (6).

2. A MEMS acoustic sensor chip according to claim 1, characterized in that: The hole (5a) extends into the bottom electrode layer (4) to a certain depth.

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