Differential capacitive ciliary hydrophone and method for manufacturing the same

Abstract

The present invention provides a differential capacitive ciliary hydrophone and a manufacturing method thereof, belonging to the technical field of underwater sonar sensor manufacturing. The differential capacitive ciliary hydrophone structure of the present invention includes a ciliary body, a connecting beam, a central connector, an upper electrode, a passivation layer, a dielectric layer, a lower electrode, a substrate layer, etc.; the preparation method uses a COMS-MEMS monolithic integration process, and sets the structure of the device in the back-end layer of the COMS process, and the circuit signal processing electronic layer is integrated below the device structure, and each metal layer is connected by a metal tungsten plug. The differential capacitive ciliary hydrophone prepared by the COMS-MEMS monolithic integration process has the advantages of good consistency, integration, wide bandwidth, high sensitivity, easy packaging, and mass production.

Description

Technical Field

[0001] The invention relates to the technical field of CMOS-MEMS integrated sensor manufacturing, in particular to a differential capacitive ciliary hydrophone and a preparation method thereof. Background Art

[0002] At present, sound waves are the only carrier that can transmit information over long distances underwater. We mainly use hydroacoustic technology to explore and study the ocean. The hydrophone receives sound wave signals through core functional components, converts them into electrical signals, and then amplifies the electrical signals for transmission. Traditional hydrophones usually have disadvantages such as large size, poor consistency, and high cost. The differential capacitive ciliary hydrophone manufactured with integrated CMOS-MEMS technology has the advantages of wide bandwidth, high sensitivity, miniaturization, integration, good consistency, and mass production. Therefore, we urgently need to develop a CMOS-MEMS-based hydrophone with a new structure and preparation method to meet the needs of the current industry. Summary of the invention

[0003] The purpose of the present invention is to provide a hydrophone structure based on CMOS-MEMS integration, specifically a differential capacitive ciliary hydrophone.

[0004] The present invention is achieved through the following technical solutions:

[0005] A differential capacitive ciliary hydrophone comprises a substrate layer, on which a first dielectric layer, a first metal layer, a second dielectric layer, a second metal layer, ..., an (n-1)th dielectric layer, an (n-1)th metal layer, an nth dielectric layer, an nth metal layer, a polysilicon layer and a passivation layer are arranged in order from bottom to top, where n is greater than or equal to 3; a cavity is formed by etching the nth dielectric layer, the top of the cavity is the nth metal layer, the bottom is the (n-1)th metal layer, and the top of the cavity is the nth metal layer. The n metal layers form an upper electrode layer, the nth metal layer, the polysilicon layer and the passivation layer part form a central connector located in the center and four connecting beams connected around the central connector, the ciliary body is vertically fixed on the central connector, and the upper electrodes are distributed on the four connecting beams; adjacent metal layers are interconnected by tungsten plugs, the nth metal layer serves as the upper electrode layer and is provided with electrode welding points, the (n-1)th metal layer serves as the lower electrode layer, and the (n-2)th metal layer serves as the electronic layer.

[0006] As a preferred technical solution, the material of the base layer is silicon, the material of the dielectric layer is silicon oxide, the material of the metal layer is aluminum, the material of the passivation layer is silicon nitride, the material of the ciliary body is silicon, glass or resin, the shape of the ciliary body is cylinder or cuboid, and the shape of the cavity is cuboid.

[0007] As a preferred technical solution, the base layer uses a silicon wafer, which is a lightly doped P-type (100) silicon wafer with a typical doping concentration of N A ≈10 15 cm -3 .

[0008] As a preferred technical solution, a CMOS signal processing circuit is provided on the electronic layer.

[0009] Furthermore, the present invention also provides a method for preparing the above-mentioned differential capacitive ciliary hydrophone, comprising the following steps:

[0010] Step 1: Select a silicon wafer as the starting base layer, and use the CMOS process to complete the production of the CMOS active area, n dielectric layers and n metal layers on the base layer, and each metal layer is interconnected by a tungsten plug; wherein the nth metal layer is used as the upper electrode layer, the polysilicon layer is used as the main layer for making the central connector, the connecting beam and the electrode, the nth dielectric layer is used as the main layer for making the cavity, the (n-2)th metal layer is used as the electronic layer, the (n-1)th metal layer is used as the lower electrode layer, and the nth and (n-1)th metal layers are patterned after preparation;

[0011] Step 2: depositing a polysilicon layer and a passivation layer, a polysilicon layer and a passivation layer on the nth metal layer and patterning them to form a connecting beam and a central connecting body structure;

[0012] Step 3: forming a cavity in the nth dielectric layer by dry etching, so that the central connector and the connecting beam are suspended;

[0013] Step 4: Electrical welding, lead out electrode welding points, adhere the cilia to the central mass block through secondary integration, and finally obtain the differential capacitive cilia hydrophone.

[0014] As a preferred technical solution, in step 1, the CMOS process includes a 0.18um process.

[0015] As a preferred technical solution, the material of the metal layer is aluminum, the dielectric layer is silicon dioxide deposited by chemical vapor deposition, and the passivation layer is silicon nitride deposited by chemical vapor deposition.

[0016] As a preferred technical solution, the silicon dioxide of the dielectric layer is phosphorus or boron doped silicon dioxide.

[0017] As a preferred technical solution, in step 3, the dry etching is carried out by etching with hydrofluoric acid gas.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) The differential capacitive ciliary hydrophone of the present invention has the characteristics of good reliability, small size, wide frequency band, high sensitivity, low manufacturing cost, and easy mass production;

[0020] 2) The differential capacitive ciliary hydrophone of the present invention has better performance, allows for smaller packaging, and further reduces packaging and instrument costs, while having greater scalability and applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below; it should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 Schematic diagram of the overall structure of the differential capacitive ciliary hydrophone of the present invention (not packaged).

[0023] Figure 2 The schematic diagram of the Wheatstone bridge formed by the differential capacitive ciliary hydrophone electrodes of the present invention.

[0024] Figure 3 It is a schematic side view of the overall structure of the differential capacitive ciliary hydrophone of the present invention (not packaged).

[0025] Figure 4 This is a schematic diagram of the cross-sectional structure of the differential capacitive ciliary hydrophone of the present invention (not packaged).

[0026] In the figure: 1-base layer, 2-polysilicon layer, 3-passivation layer, 4-cavity, 5-central connector, 6-connecting beam, 7-ciliary body, 8-electrode welding point, 9-tungsten plug;

[0027] l1-the first dielectric layer, ln-the nth dielectric layer, m1-the first metal layer, m(n-1)-the (n-1)th metal layer, mn-the nth metal layer;

[0028] c1, c2, c3, c4, c5, c6, c7, and c8 are upper electrodes, and C1, C2, C3, C4, C5, C6, C7, and C8 are lower electrodes. DETAILED DESCRIPTION

[0029] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field without creative work, including the embodiments of the present invention, belong to the protection scope of the present invention.

[0030] In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate the orientation or position relationship as shown in the integrated drawings, which 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 operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance, quantity or position.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] like Figures 1 to 4As shown, a differential capacitive ciliary hydrophone comprises a substrate layer 1, on which are arranged in order from bottom to top a first dielectric layer l1, a first metal layer m1, a second dielectric layer, a second metal layer, ..., an (n-1)th dielectric layer, an (n-1)th metal layer m(n-1), an nth dielectric layer ln, an nth metal layer mn, a polysilicon layer 2 and a passivation layer 3, where n≥3; a cavity 4 is formed by etching on the nth dielectric layer ln, the top of the cavity 4 is the nth metal layer mn, the bottom is the (n-1)th metal layer m(n-1), and the nth metal layer mn, the polysilicon layer 2 and the passivation layer 3 on the top of the cavity 4 are partially formed A central connector 5 is located in the center and four connecting beams 6 are connected around the central connector 5. A ciliary body 7 is vertically fixed on the central connector 5. Upper electrodes c1, c2, c3, c4, c5, c6, c7, and c8 are distributed on the four connecting beams 6. Adjacent metal layers are interconnected through tungsten plugs 9. The nth metal layer mn is used as an electrode and an electrode welding point 8 is provided thereon. The (n-1)th metal layer m(n-1) is used as a lower electrode layer. Lower electrodes C1, C2, C3, C4, C5, C6, C7, and C8 are provided on the lower electrode layer. The (n-2)th metal layer is used as an electronic layer. A CMOS signal processing circuit is provided on the electronic layer.

[0033] In the above hydrophone structure, the material of the substrate layer 1 is silicon, the material of the dielectric layer is silicon oxide, the material of the metal layer is aluminum, the material of the passivation layer 3 is silicon nitride, the material of the ciliary body 7 is silicon, glass or resin, the shape of the ciliary body 7 is a cylinder or a cuboid, and the shape of the cavity 4 is a cuboid; wherein the substrate layer 1 is made of silicon wafer, and the silicon wafer is a lightly doped P-type (100) silicon wafer, and the typical doping concentration is N A ≈10 15 cm -3 .

[0034] The method for preparing the differential capacitive ciliary hydrophone uses the back end of line (BEOL) layer of the COMS process as the structural layer of the MEMS device, the COMS electronic layer is integrated below the MEMS device layer, and each metal layer is interconnected through a tungsten plug 9, specifically comprising the following steps:

[0035] Step 1: A silicon wafer is selected as a starting base layer 1, and a CMOS process is used to complete the production of a CMOS active area, an n-layer dielectric layer, and an n-layer metal layer on the base layer 1. Each metal layer is interconnected through a tungsten plug 9. After the n-th metal layer mn is prepared, it is patterned to form upper electrodes c1, c2, c3, c4, c5, c6, c7, and c8. After the n-1-th metal layer m(n-1) is prepared, it is patterned to form lower electrodes C1, C2, C3, C4, C5, C6, C7, and C8. Among them, the n-th metal layer mn is used as the main layer for making the central connector 5, the connecting beam 6, and the electrode, the n-th dielectric layer ln is used as the main layer for making the cavity 4, the (n-2)-th metal layer is used as the electronic layer, and the (n-1)-th metal layer m(n-1) is used as the lower electrode layer. The material of the metal layer is aluminum, and the dielectric layer is silicon dioxide deposited by chemical vapor deposition, and the silicon dioxide is phosphorus or boron doped silicon dioxide.

[0036] In this step, the base layer 1 is suitable for almost any flat substrate, such as silicon wafers, glass wafers, etc. In order to adapt to the CMOS process, a silicon wafer is selected as the base layer 1. The silicon wafer uses a lightly doped P-type (100) silicon wafer with a typical doping concentration of N A ≈10 15 cm -3 ; The CMOS process includes a 0.18um process and an advanced process with a smaller characteristic line width. The four basic micro-manufacturing technologies of the CMOS process: deposition, photolithography, doping and etching are combined to complete the production of the CMOS active area, n-layer dielectric layer, n-layer metal layer, polysilicon layer 2 and passivation layer 3 layer by layer; when depositing the dielectric layer, plasma enhanced chemical vapor deposition (PECVD) can be used to deposit silicon oxide; a metal layer is formed on each dielectric layer by sputtering metal aluminum, a layer of photoresist is coated on the metal layer, and the mask pattern is transferred to the photoresist by photolithography technology. The photoresist pattern is used as a mask and then the pattern of each metal layer is defined by a wet etching process to realize the functions of different metal layers; the metal layer is often used for electrical interconnection, electrode material, resistor, etc. In the present invention, the metal layer is used as an electrode, an electronic layer and a lower electrode layer.

[0037] Step 2: depositing a polysilicon layer 2 and a passivation layer 3 on the nth metal layer mn, and patterning the polysilicon layer 2 and the passivation layer 3 to form a connecting beam 6 and a central connecting body 5 structure; the passivation layer 3 is silicon nitride deposited by chemical vapor deposition.

[0038] Step 2: depositing a polysilicon layer 2 and a passivation layer 3 on the nth metal layer mn, etching the nth metal layer mn, the polysilicon layer 2 and the passivation layer 3 and patterning them to form a connecting beam 6 and a central connecting body 5 structure;

[0039] Step 3: Form a cavity 4 in the nth dielectric layer ln by dry etching, so that the central connector 5 and the connecting beam 6 are suspended in the air; wherein the dry etching is performed using hydrofluoric acid gas, and the silicon oxide in the nth dielectric layer ln is isotropically dry-etched by hydrofluoric acid gas. The hydrofluoric acid gas has a relatively high selectivity for the metal layer and will not corrode the metal layer during the dry etching process.

[0040] Step 5: Electrical welding, lead out the electrode solder joint 8, adhere the ciliary body 7 to the central connector 5 through secondary integration to obtain a differential capacitive ciliary hydrophone; lead out the electrode through wire bonding and connect the hydrophone to the PCB.

[0041] Step 6: Use a sound-transparent cap to encapsulate the hydrophone and inject silicone oil.

[0042] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A differential capacitive ciliary hydrophone, characterized in that: The invention comprises a base layer, on which a first dielectric layer, a first metal layer, a second dielectric layer, a second metal layer, ..., an (n-1)th dielectric layer, an (n-1)th metal layer, an nth dielectric layer, an nth metal layer, a polysilicon layer and a passivation layer are sequentially arranged from bottom to top, where n is greater than or equal to 3; a cavity is formed by etching the nth dielectric layer, the top of the cavity is the nth metal layer, the bottom is the (n-1)th metal layer, the nth metal layer, the polysilicon layer and the passivation layer portion at the top of the cavity are The invention is divided into a central connector located in the center and four connecting beams connected to the central connector on four sides, a ciliary body is vertically fixed on the central connector, and two connected upper electrodes are distributed on each connecting beam; adjacent metal layers are interconnected by tungsten plugs, the nth metal layer is used as the upper electrode layer and an electrode welding point is provided thereon, the (n-1)th metal layer is used as the lower electrode layer, and the lower electrode layer is provided with eight connected lower electrodes corresponding to the upper electrodes one by one, and the (n-2)th metal layer is used as the electron layer.

2. The differential capacitive ciliary hydrophone according to claim 1, characterized in that: The material of the base layer is silicon, the material of the dielectric layer is silicon oxide, the material of the metal layer is aluminum, the material of the passivation layer is silicon nitride, the material of the ciliary body is silicon, glass or resin, the shape of the ciliary body is cylindrical or rectangular, the cilia are adhered to the central connector through secondary integration, and the shape of the cavity is a rectangular parallelepiped.

3. The differential capacitive ciliary hydrophone according to claim 2, characterized in that: The base layer is made of silicon wafer, which is a lightly doped P-type (100) silicon wafer with a typical doping concentration of N A ≈10 15 cm -3 .

4. The differential capacitive ciliary hydrophone according to any one of claims 1 to 3, characterized in that: A CMOS signal processing circuit is provided on the electronic layer.

5. The method for preparing a differential capacitive ciliary hydrophone according to claim 1, characterized in that: The steps include: Step 1: A silicon wafer is selected as the starting base layer, and a CMOS process is used to complete the production of a CMOS active area, n dielectric layers, and n metal layers on the base layer. Each metal layer is interconnected through a tungsten plug; wherein the nth metal layer is used as the main layer for producing a central connector, a connecting beam, and an electrode, the nth dielectric layer is used as the main layer for producing a cavity, the (n-2)th metal layer is used as an electronic layer, the (n-1)th metal layer is used as a lower electrode layer, and the nth and (n-1)th metal layers are patterned after being prepared; Step 2: depositing a polysilicon layer and a passivation layer on the nth metal layer, and patterning the polysilicon layer and the passivation layer to form a connecting beam and a central connecting body structure; Step 3: forming a cavity in the nth dielectric layer by dry etching, so that the central connector and the connecting beam are suspended; Step 4: Electrical welding to lead out electrode welding points, and finally the differential capacitive ciliary hydrophone is obtained.

6. The method for preparing the differential capacitive ciliary hydrophone according to claim 5, characterized in that: In step 1, the CMOS process includes a 0.18um process.

7. The method for preparing the differential capacitive ciliary hydrophone according to claim 5, characterized in that: The metal layer is made of aluminum, the dielectric layer is made of silicon dioxide deposited by chemical vapor, and the passivation layer is made of silicon nitride deposited by chemical vapor.

8. The method for preparing the differential capacitive ciliary hydrophone according to claim 7, characterized in that: The silicon dioxide of the dielectric layer is phosphorus or boron doped silicon dioxide.

9. The method for preparing the differential capacitive ciliary hydrophone according to claim 5, characterized in that: In step 3, dry etching is performed using hydrofluoric acid gas.

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