A wafer-level packaging structure and method for micro-electromechanical system microphone

Abstract

The present invention discloses a wafer-level packaging structure and method for a micro-electromechanical system microphone, including: an independent chip, the independent chip includes a first wafer and a second wafer; the first wafer contains a dedicated integrated circuit chip unit, and the first surface of the first wafer is provided with a plurality of first pads; the second wafer is located on the first wafer, the second wafer contains a micro-electromechanical system microphone chip unit, the third surface of the second wafer is provided with a plurality of second pads, and the second wafer is provided with a plurality of conductive through holes; the first wafer is provided with a plurality of first through holes, a first insulating layer and a wiring layer; the first through hole exposes part or all of the first pads; the first insulating layer is provided on the side wall of the first through hole; the wiring layer is provided on the first insulating layer, and the wiring layer is electrically connected to the first pad. The technical solution provided by the embodiment of the present invention effectively reduces the product size.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of microphone technology, and in particular to a wafer-level packaging structure and method for a micro-electromechanical system microphone. Background Art

[0002] Micro-Electro-Mechanical System (MEMS) microphones are microphones manufactured based on MEMS technology. They convert voice signals into electrical signals and are widely used in mobile phones, computers, cameras, camcorders, and smart home products.

[0003] The MEMS microphone packaging structure includes a circuit board. A single MEMS microphone chip and a single Application Specific Integrated Circuit (ASIC) chip are electrically connected by gold wires and are arranged on the circuit board. The MEMS microphone chip transmits the electrical signal converted from the sound signal to the ASIC chip, and the ASIC chip processes and amplifies the electrical signal.

[0004] The current MEMS microphone packaging structure cannot meet the needs of product miniaturization. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a wafer-level packaging structure and method for a micro-electromechanical system microphone, which effectively reduces the product size.

[0006] In a first aspect, an embodiment of the present invention provides a micro-electromechanical system microphone wafer-level packaging structure, comprising:

[0007] An independent chip, wherein the independent chip includes a first wafer and a second wafer;

[0008] The first wafer has a first surface and a second surface opposite to the first surface, the first wafer contains a dedicated integrated circuit chip unit, and the first surface of the first wafer is provided with a plurality of first pads, and the first pads are electrically connected to the dedicated integrated circuit chip unit;

[0009] The second wafer is located on the first wafer, wherein the second wafer has a third surface and a fourth surface opposite to the third surface, the second wafer contains a micro-electromechanical system microphone chip unit, the third surface of the second wafer is provided with a plurality of second pads, the second pads are electrically connected to the micro-electromechanical system microphone chip unit, and the second wafer is provided with a plurality of conductive through holes, wherein one conductive through hole exposes part or all of one second pad located on the third surface, and one conductive through hole covers part or all of one first pad;

[0010] The first wafer is provided with a plurality of first through holes, a first insulating layer and a wiring layer; the first through holes expose part or all of the first pads; the first insulating layer is arranged on the side walls of the first through holes; the wiring layer is arranged on the first insulating layer, and the wiring layer is electrically connected to the first pads.

[0011] In a second aspect, an embodiment of the present invention provides a micro-electromechanical system microphone wafer-level packaging method, comprising:

[0012] Prepare a first wafer, wherein the first wafer has a first surface and a second surface opposite to the first surface, the first wafer contains a plurality of ASIC chip units, the first surface of the first wafer is provided with a plurality of first pads, and the first pads are electrically connected to the ASIC chip units;

[0013] Prepare a second wafer, wherein the second wafer has a third surface and a fourth surface opposite to the third surface, the second wafer contains a plurality of micro-electromechanical system microphone chip units, the third surface of the second wafer is provided with a plurality of second pads, the second pads are electrically connected to the micro-electromechanical system microphone chip units, and the second wafer is provided with a plurality of conductive through holes, one of the conductive through holes exposes a part or all of one of the second pads located on the third surface;

[0014] Disposing the second wafer on the first wafer, wherein the fourth surface of the second wafer is disposed on the first surface of the first wafer, and a conductive through hole covers part or all of a first pad;

[0015] Forming at least one first through hole in the first wafer, wherein the first through hole exposes part or all of the first pad;

[0016] forming a first insulating layer on a sidewall of the first through hole;

[0017] forming a wiring layer on the first insulating layer, wherein the wiring layer is electrically connected to the first pad;

[0018] A plurality of the micro-electromechanical system microphone chip units and a plurality of the ASIC chip units are cut along the first through hole to form a plurality of independent chips, each of which includes a micro-electromechanical system microphone chip unit and a ASIC chip unit.

[0019] In this embodiment, the independent chip includes a first wafer and a second wafer; the first wafer includes an integrated circuit chip unit, the second wafer includes a micro-electromechanical system microphone chip unit, the second wafer is located on the first wafer, the micro-electromechanical system microphone chip unit is electrically connected to the second pad, the micro-electromechanical system microphone chip unit transmits the electric signal converted from the sound signal to the second pad, the conductive through hole transmits the electric signal of the second pad to the first pad set on the first surface of the first wafer, the first pad transmits the electric signal to the dedicated integrated circuit chip unit for signal processing and amplification, the processed electric signal is transmitted by the dedicated integrated circuit chip unit to another first pad, and the wiring layer transmits the electric signal of the first pad set on the first surface of the first wafer to the second surface of the first wafer so as to be electrically connected to the external circuit. Compared with the packaging structure of the prior art, the horizontal packaging size is reduced, and the technical solution in this embodiment realizes the electrical connection between the micro-electromechanical system microphone chip unit and the integrated circuit chip unit through the conductive through hole, and compared with the packaging structure of the prior art, the gold wire connection is used, which saves costs and simplifies the process of the preparation process. Moreover, the technical solution in this embodiment uses a first wafer and a second wafer to complete the packaging of an integrated circuit chip unit and a micro-electromechanical system microphone chip unit, which is called wafer-level packaging, wherein the first wafer can include multiple integrated circuit chip units and the second wafer can include multiple micro-electromechanical system microphone chip units. By cutting the first wafer and the second wafer, the packaging of multiple independent chips can be completed at the same time, which greatly improves the packaging efficiency compared to the prior art in which independent micro-electromechanical system microphone chips and independent special integrated circuit chips are laid flat on the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of a micro-electromechanical system microphone packaging structure in the prior art;

[0021] Figure 2 A schematic structural diagram of a wafer-level packaging structure of a micro-electromechanical system microphone provided by an embodiment of the present invention;

[0022] Figure 3 A schematic structural diagram of another MEMS microphone wafer-level packaging structure provided by an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of a process flow of a micro-electromechanical system microphone wafer-level packaging method provided by an embodiment of the present invention;

[0024] Figure 5-Figure 15 A cross-sectional view corresponding to each step of a wafer-level packaging method for a micro-electromechanical system microphone provided by an embodiment of the present invention;

[0025] Fig.16A schematic flow chart of another method for wafer-level packaging of a micro-electromechanical system microphone provided by an embodiment of the present invention;

[0026] Fig.17 A schematic flow chart of another method for wafer-level packaging of a micro-electromechanical system microphone provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0028] As mentioned in the background above, the current MEMS microphone packaging structure cannot meet the demand for product miniaturization. Figure 1 The existing MEMS microphone packaging structure includes an independent MEMS microphone chip 10, an independent ASIC chip 11, a housing 12 and a circuit board 13. The independent MEMS microphone chip 10 and the independent ASIC chip 11 are electrically connected by gold wires 14, and are laid flat on the circuit board 13, resulting in a large size of the packaging structure in the horizontal direction, resulting in a large volume of the packaging structure, which cannot meet the needs of product miniaturization.

[0029] In view of the above technical problems, the embodiments of the present invention provide the following technical solutions:

[0030] Figure 2 A schematic diagram of a wafer-level packaging structure of a micro-electromechanical system microphone provided by an embodiment of the present invention. Figure 2The micro-electromechanical system microphone wafer-level packaging structure includes: an independent chip 20, the independent chip 20 includes a first wafer 21 and a second wafer 22; the first wafer 21 has a first surface 210A and a second surface 210B opposite to the first surface 210A, the first wafer 21 contains a dedicated integrated circuit chip unit 21A, the first surface 210A of the first wafer 21 is provided with a plurality of first pads 211, and the first pads 211 are electrically connected to the dedicated integrated circuit chip unit 21A; the second wafer 22 is located on the first wafer 21, wherein the second wafer 22 has a third surface 220A and a fourth surface 220B opposite to the third surface 220A, the second wafer 22 contains the micro-electromechanical system microphone chip unit 22A, the second The third surface 220A of the wafer 22 is provided with a plurality of second pads 221, and the second pads 221 are electrically connected to the micro-electromechanical system microphone chip unit 22A. A plurality of conductive through holes 222 are provided in the second wafer, and a conductive through hole 222 exposes part or all of a second pad 221 located on the third surface 220A, and a conductive through hole 222 covers part or all of a first pad 211; the first wafer 21 is provided with a plurality of first through holes 212, a first insulating layer 213 and a wiring layer 214; the first through hole 212 exposes part or all of the first pad 211; the first insulating layer 213 is provided on the side wall of the first through hole 212; the wiring layer 214 is provided on the first insulating layer 213, and the wiring layer 214 is electrically connected to the first pad 211.

[0031] In this embodiment, the second pad 221 is equivalent to the lead-out electrode of the micro-electro-mechanical system microphone chip unit 22A, and the second pad 221 is electrically connected to two electrodes of the micro-electro-mechanical system microphone chip unit 22A.

[0032] The wiring layer 214 may include one or more layers of metal. The preparation process of the wiring layer 214 may be, for example, a magnetron sputtering process. The micro-electromechanical system microphone chip unit 22A transmits the electric signal converted from the sound signal to the second pad 221, the conductive via 222 transmits the electric signal of the second pad 221 to the first pad 211 set on the first surface 210A of the first wafer 21, the first pad 211 transmits the electric signal to the dedicated integrated circuit chip unit 21A for signal processing and amplification, the processed electric signal is transmitted by the dedicated integrated circuit chip unit 21A to another first pad 211, and the wiring layer 214 transmits the electric signal of the first pad 211 set on the first surface 210A of the first wafer 21 to the second surface 210B of the first wafer 21 so as to be electrically connected to the external circuit.

[0033] It should be noted that the wiring layer 214 formed by multiple layers of metal can form a better electrical connection with the first pad 211 than the wiring layer 214 formed by a single layer of metal. Exemplarily, titanium metal is sputtered on the surface of the first insulating layer 213, and then a layer of copper metal is sputtered on the surface of the titanium metal by magnetron sputtering, so as to complete the production of the wiring layer 214.

[0034] In this embodiment, the independent chip 20 includes a first wafer 21 and a second wafer 22; the first wafer 21 includes an integrated circuit chip unit 21A, the second wafer 22 includes a micro-electromechanical system microphone chip unit 22A, the second wafer 22 is located on the first wafer 21, the micro-electromechanical system microphone chip unit 22A is electrically connected to the second pad 221, the micro-electromechanical system microphone chip unit 22A transmits the electrical signal converted from the sound signal to the second pad 221, the conductive through hole 222 transmits the electrical signal of the second pad 221 to the first pad 211 set on the first surface 210A of the first wafer 21, the first pad 211 transmits the electrical signal to the dedicated integrated circuit chip unit 21A for signal processing and amplification, the processed electrical signal is transmitted by the dedicated integrated circuit chip unit 21A to another first pad 211, and the wiring layer 214 transmits the electrical signal of the first pad 211 set on the first surface 210A of the first wafer 21 to the second surface 210B of the first wafer 21 so as to be electrically connected to an external circuit. Compared with the packaging structure of the prior art, the independent MEMS microphone chip 10 and the independent ASIC chip 11 are laid flat on the circuit board 14, which reduces the horizontal packaging size. In the technical solution of this embodiment, the electrical connection between the MEMS microphone chip unit 22A and the IC chip unit 21A is realized through the conductive through hole 222. Compared with the packaging structure of the prior art using gold wire connection, the cost is saved and the preparation process is simplified. In addition, the technical solution of this embodiment uses the first wafer 21 and the second wafer 22 to complete the packaging of the IC chip unit 21A and the MEMS microphone chip unit 22A, which is called wafer-level packaging. The first wafer 21 can contain multiple IC chip units 21A and the second wafer can contain multiple MEMS microphone chip units 22A. By cutting the first wafer 21 and the second wafer 22, the packaging of multiple independent chips can be completed at the same time. Compared with the prior art, the independent MEMS microphone chip 10 and the independent ASIC chip 11 are laid flat on the circuit board 14, which greatly improves the packaging efficiency.

[0035] In the above technical solution, the wiring layer 214 transmits the electrical signal of the first pad 211 provided on the first surface 210A of the first wafer 21 to the second surface 210B of the first wafer 21 so as to be electrically connected to the external circuit. In actual situations, part of the wiring layer 214 is in contact with the external circuit to achieve electrical connection. In order to protect the part of the wiring layer 214 that is not in contact with the external circuit, the embodiment of the present invention provides the following technical solution: Figure 3 A schematic diagram of another MEMS microphone wafer-level packaging structure provided by an embodiment of the present invention. Figure 3 The first wafer 21 is further provided with a second insulating layer 215 disposed on the wiring layer 214 . The second insulating layer 215 includes at least one first opening structure 215A. Each first opening structure 215A exposes a portion of the wiring layer 214 .

[0036] Specifically, the second insulating layer 215 includes at least one first opening structure 215A. Each first opening structure 215A exposes a portion of the wiring layer 214 to contact with an external circuit to achieve electrical connection, so as to protect a portion of the wiring layer 214 that is not in contact with the external circuit.

[0037] Alternatively, see Figure 3 The MEMS microphone wafer-level packaging structure further includes a cover plate 30 disposed on the third surface 220A of the second wafer 22 . The cover plate 30 includes a second opening structure 31 . The second opening structure 31 exposes the MEMS microphone chip unit 22A.

[0038] Specifically, the sound enters from the second opening structure 31, and the micro-electromechanical system microphone chip unit 22A converts the sound signal into an electrical signal, which is transmitted to the integrated circuit chip unit 21A in the first wafer 21 through the second pad 221 and the conductive through hole 222. The wiring layer 214 transmits the electrical signal of the first pad 211 provided on the first surface 210A of the first wafer 21 to the second surface 210B of the first wafer 21, thereby realizing electrical connection with the external circuit.

[0039] In the above technical solution, the conductive via 222 transmits the electrical signal of the second pad 221 to the integrated circuit chip unit 21A in the first wafer 21. Figure 3 The conductive through hole 222 includes: a second through hole 222A, which is arranged in the second wafer 22, and a second through hole 222A exposes a second pad 221 located partially or completely on the third surface 220A; a third insulating layer 222B, which is arranged on the surface of the side wall of the second through hole 222A; a conductive column 222C, which is arranged on the surface of the third insulating layer 222B away from the side wall of the second through hole 222A, and the second pad 221 covers the conductive column.

[0040] Specifically, the third insulating layer 222B insulates the conductive pillar 222C and the second wafer 22. The conductive pillar 222C, the third insulating layer 222B and the second wafer 22 constitute an equivalent capacitor, wherein the second wafer 22 is a high-resistance silicon material, so that the capacitance value of the equivalent capacitor is relatively low, and the interference to the micro-electromechanical system microphone chip unit 22A is relatively small. The conductive pillar 222C is electrically connected to the second pad 221 to enable the conductive through hole 222 to transmit the electrical signal of the second pad 221 to the integrated circuit chip unit 21A in the first wafer 21 through the first pad 211, and then to the wiring layer 214 through the first pad 211. The wiring layer 214 transmits the electrical signal of the first pad 211 to the second surface 210B of the first wafer 21 to achieve electrical connection with the external circuit.

[0041] Alternatively, see Figure 3 The second wafer 22 also includes a groove 22B corresponding to the micro-electromechanical system microphone chip unit 22A, and a micro-electromechanical system microphone chip unit 22A is suspended above a groove 22B, wherein the micro-electromechanical system microphone chip unit 22A is close to the third surface 220A, and the groove 22B is located on the fourth surface 220B.

[0042] The sound signal can propagate in the groove 22B, and the groove 22B can reduce the damping of the air discharge in the micro-electro-mechanical system microphone chip unit 22A, thereby improving the signal-to-noise ratio of the micro-electro-mechanical system microphone chip unit 22A. The larger the volume of the groove 22B, the higher the signal-to-noise ratio of the micro-electro-mechanical system microphone chip unit 22A, and the better the product performance.

[0043] In the above technical solution, the MEMS microphone chip unit 22A converts the sound signal into an electrical signal, transmits the electrical signal to the first pad 211 through the through hole 222, and the wiring layer 214 transmits the electrical signal to the second surface 210B of the first wafer 21 to achieve electrical connection with the external circuit. The MEMS microphone chip unit 22A can be a capacitive microphone or a piezoelectric microphone. When the MEMS microphone chip unit 22A is a capacitive microphone type, the MEMS microphone chip unit 22A includes a diaphragm and a back plate, the diaphragm is electrically connected to a second pad 221, and the back plate is electrically connected to another second pad 221.

[0044] The specific principle is as follows: the capacitive microphone chip is used to change the distance between the diaphragm and the back plate according to the received sound signal, the capacitance value of the diaphragm and the back plate changes, and the corresponding electrical signal is output between the diaphragm and the back plate.

[0045] When the MEMS microphone chip unit 22A is a piezoelectric microphone, the MEMS microphone chip unit includes a piezoelectric module, which includes a first electrode, a piezoelectric film, and a second electrode stacked in sequence from bottom to top. The first electrode is electrically connected to a second pad 221, and the second electrode is electrically connected to another second pad 221.

[0046] The specific principle is as follows: the piezoelectric film is used to deform according to the received sound signal, and opposite charges appear on the first surface and the second surface, so that a potential difference is formed between the first electrode and the second electrode as the corresponding electrical signal. The stronger the sound signal, the greater the voltage value corresponding to the electrical signal.

[0047] The micro-electromechanical system microphone chip unit 22A converts the sound signal into an electrical signal, and transmits it to the integrated circuit chip unit 21A in the first wafer 21 through the second pad 221 and the conductive through hole 222. The wiring layer 214 transmits the electrical signal of the first pad 211 set on the first surface 210A of the first wafer 21 to the second surface 210B of the first wafer 21, thereby realizing electrical connection with the external circuit.

[0048] Based on the same concept, an embodiment of the present invention further provides a wafer-level packaging method for a micro-electromechanical system microphone. Figure 4 A flow chart of a method for wafer-level packaging of a micro-electromechanical system microphone is provided. Figure 5-Figure 15 The embodiment of the present invention also provides a cross-sectional view corresponding to each step of a wafer-level packaging method for a micro-electromechanical system microphone. Figure 4 , the method comprises the following steps:

[0049] Step 110, prepare a first wafer, the first wafer having a first surface and a second surface opposite to the first surface, the first wafer containing a plurality of ASIC chip units, the first surface of the first wafer being provided with a plurality of first pads, the first pads being electrically connected to the ASIC chip units.

[0050] See also Figure 5 , prepare a first wafer 21, the first wafer 21 has a first surface 210A and a second surface 210B opposite to the first surface 210A, the first wafer 21 contains a plurality of ASIC chip units 21A, the first surface 210A of the first wafer 21 is provided with a plurality of first pads 211, and the first pads 211 are electrically connected to the ASIC chip units 21A. The ASIC chip units 21A are, for example, formed on the first wafer 21 through multiple photolithography, ion implantation, etching, and evaporation processes to form a circuit structure consisting of multilayer electronic components with specific functions. The first pads 211 are equivalent to the lead-out electrodes of the ASIC chip units 21A.

[0051] Step 120, prepare a second wafer, the second wafer having a third surface and a fourth surface opposite to the third surface, the second wafer containing a plurality of micro-electromechanical system microphone chip units, the third surface of the second wafer is provided with a plurality of second pads, the second pads are electrically connected to the micro-electromechanical system microphone chip units, the second wafer is provided with a plurality of conductive through holes, a conductive through hole exposes a second pad located partially or entirely on the third surface.

[0052] See also Figure 6 , prepare a second wafer 22, the second wafer 22 has a third surface 220A and a fourth surface 220B opposite to the third surface 220A, the second wafer 22 contains a plurality of MEMS microphone chip units 22A, the third surface 220A of the second wafer 22 is provided with a plurality of second pads 221, the second pads 221 are electrically connected to the MEMS microphone chip unit 22A, the second wafer 22 is provided with a plurality of conductive through holes 222, a conductive through hole 222 exposes a second pad 221 partially or entirely located on the third surface 220A. The second pad 221 is equivalent to the lead-out electrode of the MEMS microphone chip unit 22A, and the second pad 221 is electrically connected to the two electrodes of the MEMS microphone chip unit 22A.

[0053] Step 130 , disposing the second wafer on the first wafer, wherein the fourth surface of the second wafer is disposed on the first surface of the first wafer, and a conductive through hole covers part or all of a first pad.

[0054] See also Figure 7 , the second wafer 22 is disposed on the first wafer 21 , wherein the fourth surface 220B of the second wafer 22 is disposed on the first surface 210A of the first wafer 21 , and a conductive through hole 222 covers part or all of a first pad 211 .

[0055] Optionally, step 140 further includes: forming a protective film layer on the third surface of the second wafer before forming at least one first through hole in the first wafer and exposing part or all of the first pad through the first through hole.

[0056] See also Figure 8 , a protective film layer 23 is formed on the third surface 220A of the second wafer 22. Optionally, the protective film layer 23 is formed on the third surface 220A of the second wafer 22 by a bonding process. The film layer between the protective film layer 23 and the third surface 220A of the second wafer 22 is a bonding layer. The protective film layer 23 is to improve the mechanical properties of the device and prevent the subsequent operations performed on the first wafer 21 from damaging the first wafer 21 and the second wafer 22.

[0057] Step 140 : forming at least one first through hole in the first wafer, wherein the first through hole exposes a portion or all of the first pad.

[0058] See also Fig. 9 At least one first through hole 212 is formed in the first wafer 21, and the first through hole 212 exposes part or all of the first pad 211. The first through hole 212 may be formed by an etching process.

[0059] Optionally, before forming at least one first through hole 212 in the first wafer 21 and exposing a part or all of the first pads 211 through the first through hole 212 , the first wafer 21 may be thinned. The thinning operation may reduce the difficulty of forming the first through hole 212 .

[0060] Step 150 : forming a first insulating layer on the sidewall of the first through hole.

[0061] See also Fig.10 A first insulating layer 213 is formed on the sidewall of the first through hole 212. The first insulating layer 213 can be made of silicon oxide or silicon nitride.

[0062] Step 160: Form a wiring layer on the first insulating layer, wherein the wiring layer is electrically connected to the first pad.

[0063] See also Fig.11 , a wiring layer 214 is formed on the first insulating layer 213, and the wiring layer 214 is electrically connected to the first pad 211. Specifically, the micro-electromechanical system microphone chip unit 22A transmits the electric signal converted from the sound signal to the second pad 221, and the conductive through hole 222 transmits the electric signal of the second pad 221 to the first pad 211 set on the first surface 210A of the first wafer 21, and the first pad 211 transmits the electric signal to the dedicated integrated circuit chip unit 21A for signal processing and amplification, and the processed electric signal is transmitted from the dedicated integrated circuit chip unit 21A to another first pad 211, and the wiring layer 214 transmits the electric signal of the first pad 211 set on the first surface 210A of the first wafer 21 to the second surface 210B of the first wafer 21 so as to be electrically connected to the external circuit. It should be noted that the wiring layer 214 formed by multiple layers of metal can form a better electrical connection with the first pad 211 than the wiring layer 214 formed by one layer of metal. Exemplarily, metal titanium is sputtered on the surface of the first insulating layer 213 , and then a layer of metal copper is sputtered on the surface of the metal titanium by magnetron sputtering, thereby completing the manufacturing of the wiring layer 214 .

[0064] Optionally, after forming a wiring layer 214 on the first insulating layer 213 and electrically connecting the wiring layer 214 to the first pad 211, the following further includes: Fig.12A second insulating layer 215 is formed on the wiring layer 214, and the second insulating layer 215 includes at least one first opening structure 215A, and each first opening structure 215A exposes a portion of the wiring layer 214. The second insulating layer 215 includes at least one first opening structure 215A, and each first opening structure 215A exposes a portion of the wiring layer 214 to contact with an external circuit to achieve electrical connection, so as to protect the portion of the wiring layer 214 that is not in contact with the external circuit. The second insulating layer 215 can be silicon oxide or silicon nitride.

[0065] Optionally, a second insulating layer 215 is formed on the wiring layer 214, and the second insulating layer 215 includes at least one first opening structure 215A, and each first opening structure 215A exposes a portion of the wiring layer 214, and further includes:

[0066] See also Fig.13 , remove the protective film layer 23.

[0067] See also Fig.14 , a cover plate 30 is formed on the third surface 220A of the second wafer 22, and the cover plate 30 includes a plurality of second opening structures 31, and each second opening structure 31 exposes a micro-electromechanical system microphone chip unit 22A. Specifically, the sound enters from the second opening structure 31, and the micro-electromechanical system microphone chip unit 22A converts the sound signal into an electrical signal, which is transmitted to the integrated circuit chip unit 21A in the first wafer 21 through the second pad 221 and the conductive through hole 222. The wiring layer 214 transmits the electrical signal of the first pad 211 set on the first surface 210A of the first wafer 21 to the second surface 210B of the first wafer 21, thereby realizing electrical connection with the external circuit. The cover plate 30 can be formed on the third surface 220A of the second wafer 22 by a bonding process.

[0068] Step 170: cutting a plurality of MEMS microphone chip units and a plurality of ASIC chip units along the first through hole to form a plurality of independent chips, each independent chip including a MEMS microphone chip unit and an ASIC chip unit.

[0069] See also Fig.15 , along the first through hole 212, multiple MEMS microphone chip units and multiple ASIC chip units are cut to form multiple independent chips 20, each independent chip 20 includes a MEMS microphone chip unit 22A and a ASIC chip unit 21A.

[0070] In this embodiment, the independent chip 20 includes a first wafer 21 and a second wafer 22; the first wafer 21 includes an integrated circuit chip unit 21A, the second wafer 22 includes a micro-electromechanical system microphone chip unit 22A, the second wafer 22 is located on the first wafer 21, the micro-electromechanical system microphone chip unit 22A is electrically connected to the second pad 221, the micro-electromechanical system microphone chip unit 22A transmits the electrical signal converted from the sound signal to the second pad 221, the conductive through hole 222 transmits the electrical signal of the second pad 221 to the first pad 211 set on the first surface 210A of the first wafer 21, the first pad 211 transmits the electrical signal to the dedicated integrated circuit chip unit 21A for signal processing and amplification, the processed electrical signal is transmitted by the dedicated integrated circuit chip unit 21A to another first pad 211, and the wiring layer 214 transmits the electrical signal of the first pad 211 set on the first surface 210A of the first wafer 21 to the second surface 210B of the first wafer 21 so as to be electrically connected to an external circuit. Compared with the packaging structure of the prior art, the independent MEMS microphone chip 10 and the independent ASIC chip 11 are laid flat on the circuit board 14, which reduces the horizontal packaging size. In the technical solution of this embodiment, the electrical connection between the MEMS microphone chip unit 22A and the IC chip unit 21A is realized through the conductive through hole 222. Compared with the packaging structure of the prior art using gold wire connection, the cost is saved and the preparation process is simplified. In addition, the technical solution of this embodiment uses the first wafer 21 and the second wafer 22 to complete the packaging of the IC chip unit 21A and the MEMS microphone chip unit 22A, which is called wafer-level packaging. The first wafer 21 can contain multiple IC chip units 21A and the second wafer can contain multiple MEMS microphone chip units 22A. By cutting the first wafer 21 and the second wafer 22, the packaging of multiple independent chips can be completed at the same time. Compared with the prior art, the independent MEMS microphone chip 10 and the independent ASIC chip 11 are laid flat on the circuit board 14, which greatly improves the packaging efficiency.

[0071] Fig.16 A schematic diagram of another process flow of a micro-electromechanical system microphone wafer-level packaging method provided by an embodiment of the present invention. Fig.16 Step 120 of preparing the second wafer includes:

[0072] Step 1201: Provide a second wafer, wherein the second wafer has a third surface and a fourth surface opposite to the third surface.

[0073] by Figure 3 Taking an example for illustration, a second wafer 22 is provided. The second wafer 22 has a third surface 220A and a fourth surface 220B opposite to the third surface.

[0074] Step 1202: using a micro-electromechanical system (MEMS) process to form a plurality of grooves and a plurality of MEMS microphone chip units in the second wafer, wherein a MEMS microphone chip unit is suspended above a groove, wherein the MEMS microphone chip unit is close to the third surface, and the groove is located on the fourth surface.

[0075] by Figure 3 For example, a plurality of grooves 22B and a plurality of MEMS microphone chip units 22A are formed in the second wafer 22 by using a MEMS process, and a MEMS microphone chip unit 22A is suspended above a groove 22B, wherein the MEMS microphone chip unit 22A is close to the third surface 220A, and the groove 22B is located on the fourth surface 220B. Specifically, the sound signal can be propagated in the groove 22B, and the groove 22B can reduce the damping of the air discharge in the MEMS microphone chip unit 22A, thereby improving the signal-to-noise ratio of the MEMS microphone chip unit 22A. The larger the volume of the groove 22B, the higher the signal-to-noise ratio of the MEMS microphone chip unit 22A, and the better the product performance.

[0076] Step 1203: forming a plurality of second pads on the third surface of the second wafer, wherein the second pads are electrically connected to the micro-electromechanical system microphone chip unit.

[0077] by Figure 3 For example, a plurality of second pads 221 are formed on the third surface 220A of the second wafer 22 , and the second pads 221 are electrically connected to the micro-electromechanical system microphone chip unit 22A.

[0078] Step 1204 , forming a plurality of conductive vias on the second wafer, wherein a conductive via exposes a portion or all of a second pad located on the third surface.

[0079] by Figure 3 For example, a plurality of conductive vias 222 are formed on the second wafer 22 , and a conductive via 222 exposes a portion or all of a second pad 221 located on the third surface 220A.

[0080] Fig.17 A schematic diagram of another process flow of a micro-electromechanical system microphone wafer-level packaging method provided by an embodiment of the present invention. Fig.17 Step 1204 forms a plurality of conductive vias on the second wafer, wherein a conductive via exposes a portion or all of a second pad located on the third surface and comprises:

[0081] Step 12041, forming a plurality of second through holes on the second wafer, wherein a second through hole exposes a portion or all of a second pad located on the third surface.

[0082] by Figure 3For example, a plurality of second through holes 222A are formed on the second wafer, and a second through hole 222A exposes a portion or the entirety of a second pad 221 located on the third surface 220A.

[0083] Step 12042: Form a third insulating layer on the side wall of the second through hole.

[0084] by Figure 3 Taking this as an example, a third insulating layer 222B is formed on the sidewall of the second through hole 222A.

[0085] Step 12043: forming a conductive column on a surface of the third insulating layer away from the side wall of the second through hole, and the second pad covers the conductive column.

[0086] by Figure 3 For example, a conductive pillar 222C is formed on a surface of the third insulating layer 222B away from the sidewall of the second through hole 222A, and the second pad 221 covers the conductive pillar 222C.

[0087] Specifically, the third insulating layer 222B insulates the conductive pillar 222C and the second wafer 22. The conductive pillar 222C, the third insulating layer 222B and the second wafer 22 constitute an equivalent capacitor, wherein the second wafer 22 is a high-resistance silicon material, so that the capacitance value of the equivalent capacitor is relatively low, and the interference to the micro-electromechanical system microphone chip unit 22A is relatively small. The conductive pillar 222C is electrically connected to the second pad 221 to enable the conductive through hole 222 to transmit the electrical signal of the second pad 221 to the integrated circuit chip unit 21A in the first wafer 21 through the first pad 211, and then to the wiring layer 214 through the first pad 211. The wiring layer 214 transmits the electrical signal of the first pad 211 to the second surface 210B of the first wafer 21 to achieve electrical connection with the external circuit.

[0088] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A micro-electromechanical system microphone wafer-level packaging structure, characterized in that: include: An independent chip, the independent chip comprising a first wafer and a second wafer; wherein the second wafer is high-resistance silicon; The first wafer has a first surface and a second surface opposite to the first surface, the first wafer contains a dedicated integrated circuit chip unit, and the first surface of the first wafer is provided with a plurality of first pads, and the first pads are electrically connected to the dedicated integrated circuit chip unit; The second wafer is located on the first wafer, wherein the second wafer has a third surface and a fourth surface opposite to the third surface, the second wafer contains a micro-electromechanical system microphone chip unit, the third surface of the second wafer is provided with a plurality of second pads, the second pads are electrically connected to the micro-electromechanical system microphone chip unit, and the second wafer is provided with a plurality of conductive through holes, wherein one conductive through hole exposes part or all of one second pad located on the third surface, and one conductive through hole covers part or all of one first pad; The first wafer is provided with a plurality of first through holes, a first insulating layer and a wiring layer; the first through holes expose part or all of the first pads; the first insulating layer is arranged on the side walls of the first through holes; the wiring layer is arranged on the first insulating layer, and the wiring layer is electrically connected to the first pads.

2. The wafer-level packaging structure of a micro-electromechanical system microphone according to claim 1, characterized in that: The first wafer is also provided with a second insulating layer, which is provided on the wiring layer. The second insulating layer includes at least one first opening structure, and each of the first opening structures exposes a portion of the wiring layer.

3. The wafer-level packaging structure of a micro-electromechanical system microphone according to claim 1, characterized in that: It also includes a cover plate, which is arranged on the third surface of the second wafer, and the cover plate includes a second opening structure, and the second opening structure exposes the micro-electromechanical system microphone chip unit.

4. The MEMS microphone wafer-level packaging structure according to claim 1, characterized in that: The conductive via comprises: A second through hole is disposed in the second wafer, wherein the second through hole exposes a part or all of the second pad located on the third surface; A third insulating layer is disposed on a surface of a side wall of the second through hole; A conductive column is arranged on a surface of the third insulating layer away from the side wall of the second through hole, and the second pad covers the conductive column.

5. The MEMS microphone wafer-level packaging structure according to claim 1, characterized in that: The second wafer also includes a groove corresponding to the micro-electromechanical system microphone chip unit, and the micro-electromechanical system microphone chip unit is suspended above the groove, wherein the micro-electromechanical system microphone chip unit is close to the third surface, and the groove is located on the fourth surface.

6. The MEMS microphone wafer-level packaging structure according to claim 1, characterized in that: The micro-electromechanical system microphone chip unit comprises a diaphragm and a back plate, wherein the diaphragm is electrically connected to one of the second pads, and the back plate is electrically connected to another of the second pads; or, The micro-electromechanical system microphone chip unit includes a piezoelectric module, which includes a first electrode, a piezoelectric film and a second electrode stacked in sequence from bottom to top, the first electrode is electrically connected to one of the second pads, and the second electrode is electrically connected to another of the second pads.

7. A wafer-level packaging method for a micro-electromechanical system microphone, characterized in that: include: Prepare a first wafer, wherein the first wafer has a first surface and a second surface opposite to the first surface, the first wafer contains a plurality of ASIC chip units, the first surface of the first wafer is provided with a plurality of first pads, and the first pads are electrically connected to the ASIC chip units; Prepare a second wafer, wherein the second wafer has a third surface and a fourth surface opposite to the third surface, the second wafer contains a plurality of micro-electromechanical system microphone chip units, the third surface of the second wafer is provided with a plurality of second pads, the second pads are electrically connected to the micro-electromechanical system microphone chip units, and the second wafer is provided with a plurality of conductive through holes, one of the conductive through holes exposes a part or all of one of the second pads located on the third surface; Disposing the second wafer on the first wafer, wherein the fourth surface of the second wafer is disposed on the first surface of the first wafer, and a conductive through hole covers part or all of a first pad; Forming at least one first through hole in the first wafer, wherein the first through hole exposes part or all of the first pad; forming a first insulating layer on a sidewall of the first through hole; forming a wiring layer on the first insulating layer, wherein the wiring layer is electrically connected to the first pad; A plurality of the micro-electromechanical system microphone chip units and a plurality of the ASIC chip units are cut along the first through hole to form a plurality of independent chips, each of which includes a micro-electromechanical system microphone chip unit and a ASIC chip unit.

8. The wafer-level packaging method for a MEMS microphone according to claim 7, characterized in that: After forming a wiring layer on the first insulating layer and electrically connecting the wiring layer to the first pad, the method further comprises: A second insulating layer is formed on the wiring layer, wherein the second insulating layer includes at least one first opening structure, and each of the first opening structures exposes a portion of the wiring layer.

9. The wafer-level packaging method for a MEMS microphone according to claim 8, characterized in that: The method further comprises: forming at least one first through hole in the first wafer, wherein the first through hole exposes part or all of the first pad. forming a protective film layer on the third surface of the second wafer; A second insulating layer is formed on the wiring layer, wherein the second insulating layer includes at least one first opening structure, and each of the first opening structures exposes a portion of the wiring layer, and further includes: removing the protective film layer; A cover plate is formed on the third surface of the second wafer, wherein the cover plate includes a plurality of second opening structures, and each of the second opening structures exposes one of the micro-electromechanical system microphone chip units.

10. The wafer-level packaging method for a MEMS microphone according to claim 7, characterized in that: Preparing the second wafer includes: Providing a second wafer, the second wafer having a third surface and a fourth surface opposite to the third surface; A plurality of grooves and a plurality of micro-electro-mechanical system microphone chip units are formed in the second wafer by using a micro-electro-mechanical system process, wherein one of the micro-electro-mechanical system microphone chip units is suspended above one of the grooves, wherein the micro-electro-mechanical system microphone chip unit is close to the third surface, and the groove is located on the fourth surface; forming a plurality of second pads on the third surface of the second wafer, wherein the second pads are electrically connected to the micro-electromechanical system microphone chip unit; A plurality of conductive vias are formed on the second wafer, wherein one of the conductive vias exposes a portion or all of one of the second pads located on the third surface.

11. The wafer-level packaging method for a MEMS microphone according to claim 10, characterized in that: A plurality of conductive vias are formed on the second wafer, wherein a conductive via exposes a portion or all of a second pad located on the third surface, and comprises: Forming a plurality of second through holes in the second wafer, wherein a second through hole exposes a part or all of a second pad located on the third surface; forming a third insulating layer on a side wall of the second through hole; A conductive column is formed on a surface of the third insulating layer away from the sidewall of the second through hole, and the second pad covers the conductive column.

12. The wafer-level packaging method for a MEMS microphone according to claim 7, characterized in that: The second wafer is high-resistance silicon.

Images