MEMS chip packaging structure of acoustic device and process thereof

Abstract

The invention discloses an MEMS chip packaging structure of an acoustic device and a process thereof, and the process comprises the following steps: substrate etching: arranging an electrode above the substrate, arranging a vibrating diaphragm above the electrode, and performing through etching from the middle position of the surface, far away from the electrode, of the substrate to form a back cavity so as to expose the electrode, the back cavity being located right below the electrode; meanwhile, penetrating through other parts of the etching substrate to form a circuit hole to expose the electrode; the circuit hole is filled with electroplated metal, a circuit is formed, one end of the circuit is electrically connected with the electrode, the other end of the circuit is flush with and exposed out of the surface of the substrate, in the substrate etching step, the substrate is made of one or more materials selected from a flexible material, glass and a semiconductor material, and the flexible material is made of metal. According to the invention, the electrical property of the MEMS chip is dragged from the front electrode to the back welding pin, the mounting flexibility of the MEMS chip is better, the internal circuit of the substrate replaces a routing process, the whole structure of the chip is more compact, and the requirement of device miniaturization is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and particularly relates to a MEMS chip packaging structure and process for acoustic devices. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) technology is the most popular sensor manufacturing technology today and an important driving force for the miniaturization, intelligence, and low energy consumption of sensors. MEMS technology has promoted the great development of sensors. MEMS mainly uses microelectronic technology to shape the mechanical structure of sensors in a micro-nano volume. A MEMS sensor is a device formed by packaging a second device and an application-specific integrated circuit chip (the first device) together. The second device (MEMS chip) converts sound into signal changes such as capacitance and resistance, and the first device (ASIC chip) converts signal changes such as capacitance and resistance into electrical signals, thereby realizing the function of the MEMS sensor - converting external signals into electrical signals. MEMS acoustic sensors mainly refer to silicon microphones, ultrasonic sensors, etc.

[0003] The core of a MEMS acoustic sensor is the MEMS chip. The diaphragm of the MEMS chip generates mechanical vibrations due to acoustic wave impacts, causing changes in electrical values. The electrodes of existing MEMS chips are generally arranged on the front surface of the chip, that is, the surface of the substrate where the diaphragm is located. The diaphragm requires mechanical vibration space, resulting in poor flexibility in electrically leading out the electrical connection ends of the MEMS chip. When the MEMS chip is interconnected with the ASIC chip, it is often achieved by wire bonding between the front electrode and the ASIC chip, resulting in an oversized structure size and not meeting the requirements of device miniaturization. The MEMS chip is electrically connected to other devices through the traction of the electrode metal wires on the front surface, which easily damages the extremely thin diaphragm and has a high difficulty in the electrical connection process. Summary of the Invention

[0004] To solve the above problems in the prior art, the present invention provides a MEMS chip packaging structure and process for acoustic devices.

[0005] To achieve the above object, a MEMS chip packaging process for acoustic devices proposed by the present invention includes the following steps: Substrate etching: An electrode is provided above the substrate, and a diaphragm is provided above the electrode. An etching is performed through the middle position of the surface of the substrate away from the electrode to form a back cavity to expose the electrode. The back cavity is located directly below the electrode; At the same time, other parts of the substrate are etched through to form circuit holes to expose the electrodes; Circuit electroplating: Metal filling is electroplated in the circuit holes to form a circuit. One end of the circuit is electrically connected to the electrode, and the other end of the circuit is flush with the surface of the substrate and exposed.

[0006] Further, in the substrate etching step, the material of the substrate is selected from one or more of flexible materials, glass, and semiconductor materials.

[0007] Furthermore, in the substrate etching step, an electrode is covered on the substrate, and the electrode has a porous structure.

[0008] Further, in the substrate etching step, a diaphragm is covered on the electrode, and the distance between the diaphragm and the electrode is 1 - 5 μm.

[0009] Further, in the substrate etching step, the material of the diaphragm is selected from one or more of polysilicon, silicon nitride, or metal.

[0010] Furthermore, in the circuit electroplating step, electroplated solder feet are extended on the surface of the substrate where the circuit is exposed, and the solder feet are electrically connected to the circuit.

[0011] Furthermore, in the circuit electroplating step, the diaphragm generates mechanical vibration, causing a change in the electrical value, which is sequentially transmitted through the electrode, the circuit, and the solder feet.

[0012] An MEMS chip packaging structure of an acoustic device includes a substrate, and further includes: An electrode and a diaphragm, the electrode is arranged above the substrate, and the diaphragm is arranged above the electrode; A back cavity, which is etched through from the middle position of the surface of the substrate away from the electrode to expose the electrode, and the back cavity is located directly below the diaphragm and the electrode; A circuit, which is etched through other parts of the substrate to form a circuit hole, and metal is electroplated and filled in the circuit hole to form a circuit. One end of the circuit is electrically connected to the electrode, and the other end of the circuit is flush with the surface of the substrate and exposed.

[0013] Further, the material of the substrate is selected from one or more of flexible materials, glass, and semiconductor materials.

[0014] Further, an electrode is covered on the substrate, and the electrode has a porous structure.

[0015] Furthermore, a diaphragm is covered on the electrode, and the distance between the diaphragm and the electrode is 1 - 5 μm.

[0016] Furthermore, the material of the diaphragm is selected from one or more of polysilicon, silicon nitride, or metal.

[0017] Further, electroplated solder feet are extended on the surface of the substrate where the circuit is exposed, and the solder feet are electrically connected to the circuit.

[0018] Further, the diaphragm generates mechanical vibration, causing a change in the electrical value, which is sequentially transmitted through the electrode, the circuit, and the solder feet.

[0019] An acoustic device includes the MEMS chip packaging structure of the above-mentioned acoustic device.

[0020] The beneficial effects of the present invention are as follows: By adding a circuit electroplating after substrate etching and solder pads connected to the circuit during the manufacturing process of the MEMS chip, the electrical connection of the MEMS chip is led from the electrodes on its front side to the solder pads on its back side. The MEMS chip has better mounting flexibility. The internal circuit of the substrate replaces the wire bonding process, and the entire structure of the chip is more compact, meeting the requirements of device miniaturization. Description of the Drawings

[0021] Figures 1-5 It is a cross-sectional view of the substrate etching step of the MEMS chip packaging process of an acoustic device according to the present invention; Figures 6-8 It is a cross-sectional view of the circuit electroplating step of the MEMS chip packaging process of an acoustic device according to the present invention; Figure 9 It is a cross-sectional view of the MEMS chip packaging structure of an acoustic device according to the present invention.

[0022] In the figure: 1. Substrate; 2. Electrode; 3. Diaphragm; 4. Back cavity; 5. Circuit; 6. Solder pad. Specific Embodiments

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts fall within the scope of protection of the present invention. The content of the present invention will be described below in conjunction with specific embodiments. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar components or components with the same or similar functions throughout.

[0024] In the description and claims of the present invention and the above-mentioned drawings, terms such as "first", "second", etc. are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments described herein can be implemented in an order other than that illustrated or described herein; the directional terms mentioned in the present invention, such as: up, down, left, right, front, back, inside, outside, front side, back side, side, etc., are only with reference to the directions of the drawings. The embodiments described below with reference to the drawings and the directional terms used are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention. In addition, for the various specific examples of processes and materials provided by the present invention, those of ordinary skill in the art can realize the application of other processes and / or the use of other materials.

[0025] To better understand the purpose, structure and function of the present invention, the following further describes in detail a MEMS chip packaging process for an acoustic device proposed by the present invention in conjunction with the drawings. The process includes the following steps: Substrate 1 etching: An electrode 2 is provided above the substrate 1, and a diaphragm 3 is provided above the electrode 2. An etching is carried out through the middle position of the surface of the substrate 1 away from the electrode 2 to form a back cavity 4, so as to expose the electrode 2. The back cavity 4 is located directly below the electrode 2; And at the same time, other parts of the substrate 1 are etched through to form circuit holes to expose the electrode 2; Circuit 5 electroplating: Metal filling is electroplated in the circuit holes to form a circuit 5. One end of the circuit 5 is electrically connected to the electrode 2, and the other end of the circuit 5 is flush with the surface of the substrate 1 and exposed.

[0026] The more specific processes of each process step are as follows: S1: Provide a carrier plate, which can be a resin plate commonly used in the art, and place the original substrate 1 for manufacturing the MEMS chip on the carrier plate (as Figure 1 shown); the substrate 1 can be one or more of a flexible material, glass, and semiconductor material, usually silicon. Silicon has good mechanical properties, thermal stability and good compatibility with microfabrication processes. The substrate 1 is located at the bottom layer of the MEMS chip, serving as the mechanical support of the entire structure, providing structural stability, and serving as the substrate for other components such as the electrode 2 and the back cavity 4.

[0027] S2: Cover a layer of electrode 2 on the upper surface of the substrate 1 (as Figure 2 shown). The electrodes 2 of the MEMS acoustic sensor are divided into fixed electrodes and movable electrodes. The fixed electrodes are located above or below the diaphragm 3, parallel to the diaphragm 3, and fixed on the substrate 1, while the movable electrodes are directly integrated on the surface of the diaphragm 3. The diaphragm 3 itself can serve as an electrode. In this application, the electrode 2 covers the upper surface of the substrate 1.

[0028] S3: Continue to cover a diaphragm 3 on the electrode 2 (as Figure 3 shown). In the present invention, the electrode 2 is disposed below the diaphragm 3. The electrode 2 is a fixed electrode, and the fixed electrode is designed as a porous structure to reduce air damping and allow sound waves to pass through. The distance between the diaphragm 3 and the electrode 2 is about 1-5 μm to form a variable capacitor. The diaphragm 3 is directly exposed to the external sound field. The material of the diaphragm 3 is selected from polysilicon. The polysilicon film has excellent characteristics such as high mobility like single-crystalline silicon material, compatibility with amorphous silicon thin film growth process, easy to achieve large-area growth, and low preparation cost, and is widely used in technical fields such as microelectronic devices. In addition, the polysilicon film structure is also commonly used in microelectromechanical systems (MEMS), especially as the basic vibration structure of sensor devices. The material of the diaphragm 3 can also be one or more of silicon nitride or metal, etc. The thickness of the diaphragm 3 on the MEMS chip is extremely thin, with a thickness ranging from nanometers to micrometers, sensitive to sound pressure, and its vibration displacement is proportional to the sound pressure, which is the core sensitive element of the sensor.

[0029] S4: Peel the substrate 1 from the carrier plate, turn it over up and down and remount it on the carrier plate. At this time, the diaphragm 3 contacts the carrier plate, and the bottom of the substrate 1 faces upward (as Figure 4 shown).

[0030] S5: Vertically etch at the middle position of the substrate 1 to expose the electrode 2, so that the substrate 1 becomes a ring-shaped structure with a hollow middle part. The hollow part is the back cavity 4 of the substrate 1. The back cavity 4 is located directly below the diaphragm 3. The back cavity 4 is generally cylindrical or rectangular. In the present invention, the cylindrical shape is taken as an example. The depth of the back cavity 4 is determined by the acoustic sensitivity and frequency response requirements of specific products. The structure of the back cavity 4 allows the diaphragm 3 to vibrate freely under the action of sound pressure, avoids air damping, and can balance the pressures on both sides of the diaphragm 3; and at the same time, vertically etch the remaining cylindrical ring of the substrate 1 to also expose the electrode 2 (as Figure 5 shown). Since the substrate 1 can be one or more of flexible materials, glass, semiconductor materials, usually silicon, when etching, a protective film is coated on the surface of the substrate 1 to be etched, and the position to be etched is not coated with the film for protection. In this application, anisotropic etching perpendicular to the surface of the substrate 1 is used, and the etching penetrates from the surface of the substrate 1 to the upper surface of the electrode 2, so that the surface of the electrode 2 is exposed.

[0031] The etching can be carried out by laser etching, dry etching or other etching methods. Vertical through holes are formed on the substrate by etching, and the through holes are used for vertical interconnection in multi-layer stacked packaging, such as the circuit electroplated in the circuit hole. In the present invention, laser ablation is taken as an example. Its principle is: using a high-energy laser beam to directly ablate the material, without a mask, and controlling the etching situation by adjusting parameters such as the laser irradiation frequency.

[0032] S6: After etching the cylindrical ring of the substrate 1, the holes formed by etching are filled through an electroplating process. The electroplated metal constitutes the circuit 5, and the bottom end of the circuit 5 is integrally connected to the electrode 2 (as Figure 6 shown), and electroplated solder feet 6 are extended along the surface of the substrate 1 at the top end of the electroplating (as Figure 7 shown). In the process flow of manufacturing the MEMS chip, etching the back cavity of the substrate 1 after covering the electrode 2 and the diaphragm 3 is the normal process flow of manufacturing the MEMS chip. Since the diaphragm 3 is very thin, protective measures need to be taken to protect the diaphragm 3 during the process flow, such as covering a polymer protective layer on the surface of the diaphragm 3 to prevent contamination or mechanical damage, which will not be elaborated in this invention. After peeling off the carrier plate, the manufacturing of the MEMS chip is completed (as Figure 8 shown). The diaphragm 3 generates mechanical vibrations under the impact of sound waves, causing changes in capacitance or other electrical values. The electrode 3 transmits the changed electrical values to the solder feet 6 through the circuit 5.

[0033] During the manufacturing process of the MEMS chip, electroplating the circuit 5 and the solder feet 6 is added after etching the substrate. The electrical property of the MEMS chip is led from the electrode 2 on its front side (the side where the diaphragm 3 is located) to the solder feet 6 on its back side. The MEMS chip is mounted through the solder feet 6 to achieve electrical connection. The mounting flexibility of the MEMS chip is better. By using the internal circuit 5 of the substrate 1 to replace the wire bonding process, the entire structure of the chip is more compact, meeting the requirements of device miniaturization.

[0034] Through the above MEMS chip packaging process of the acoustic device, a MEMS chip packaging structure of the acoustic device can be obtained. As Figure 9 shown, Figure 9 is a cross-sectional view of the packaging structure, including the substrate 1. The material of the substrate 1 is selected from one or more of flexible materials, glass, and semiconductor materials. It also includes: The electrode 2 and the diaphragm 3. The electrode 2 is arranged above the substrate 1. The electrode 2 has a porous structure. The diaphragm 3 is arranged above the electrode 2. The distance between the diaphragm 3 and the electrode 2 is about 1 - 5 μm. The material of the diaphragm 3 is selected from one or more of polysilicon, silicon nitride, or metal; The back cavity 4 is etched through the middle position of the surface of the substrate 1 away from the electrode 2 to expose the electrode 2. The back cavity 4 is located directly below the diaphragm 3 and the electrode 2; The circuit 5 is formed by etching through other parts of the substrate 1 to form circuit holes and filling them with electroplated metal. One end of the circuit 5 is electrically connected to the electrode 2, and the other end of the circuit 5 is flush with the surface of the substrate 1 and exposed. Electroplated solder feet 6 are extended on the surface of the substrate 1 of the exposed circuit 5, and the solder feet 6 are electrically connected to the circuit 5.

[0035] The diaphragm 3 generates mechanical vibrations under the impact of sound waves, causing changes in capacitance or other electrical values. The electrode transmits the changed electrical values to the solder feet 6 through the circuit 5.

[0036] Mount the MEMS chip packaging structure of the above acoustic device onto the working area. The MEMS chip is electrically connected to other devices (such as an ASIC chip) to realize the function of an acoustic sensor. The MEMS chip is electrically connected to the electrical interface of the ASIC chip through the solder feet 6 at the bottom of the substrate 1. The diaphragm 3 of the MEMS chip communicates with the external environment. The sound wave in the external environment is aligned with the middle position above the diaphragm 3, and the back cavity 4 is aligned with the middle position below the diaphragm 3. The ASIC chip can communicate with the external environment or not.

[0037] The working principle of a MEMS (Micro-Electro-Mechanical System) acoustic sensor is based on the conversion between mechanical vibration and electrical signal. Its core is to convert sound waves (sound signals) into electrical signals through a micro-mechanical structure. The core of the MEMS acoustic sensor is a micron-scale diaphragm 3 suspended above the back cavity 4. There is an electrode 2 between the diaphragm 3 and the substrate 1, and the electrode 2 forms a capacitive structure. When the sound wave in the external environment acts on the diaphragm 3, the diaphragm 3 will undergo mechanical vibration with the change of sound pressure. The back cavity 4 is arranged directly below the diaphragm 3, and the back cavity 4 provides a vibration space and acoustic damping for the diaphragm 3, adjusting the mechanical response of the diaphragm 3. The mechanical vibration of the diaphragm 3 causes the distance between the electrode 2 and the substrate 1 to change, and the electrical value of the electrode 2 changes accordingly, such as the capacitance value C. The capacitance value C is determined by the formula C = εA / d (where ε is the dielectric constant, A is the electrode area, and d is the plate spacing, and the plate spacing refers to the spacing between the electrode 2 and the substrate 1). The change in the electrical value of the electrode 2 is transmitted through the circuit 5 and the solder feet 6 to the ASIC chip electrically connected to the MEMS chip for processing. The application-specific integrated circuit (ASIC) integrated in the sensor is responsible for processing these changes in electrical values. The ASIC chip provides a bias voltage (DC voltage) for the capacitive structure, converts the capacitance change into a charge change, converts the weak charge into a voltage signal through a charge amplifier, and converts the analog voltage signal into a digital signal for output, thus playing the role of an acoustic sensor.

[0038] An acoustic device includes the MEMS chip packaging structure of the above acoustic device.

[0039] The beneficial effects of the present invention are as follows: By adding the electroplated circuit 5 after etching the substrate 1 and the solder feet 6 connected to the circuit 5 during the manufacturing process of the MEMS chip, the electrical connection of the MEMS chip is led from the electrode 2 on its front side (the side where the diaphragm 3 is located) to the solder feet 6 on its back side. The solder feet 6 serve as a medium for the MEMS chip to be mounted and electrically connected to other devices, and the mounting flexibility of the MEMS chip is better. The internal circuit 5 of the substrate 1 replaces the wire bonding process, and the entire structure of the chip is more compact, meeting the requirements of device miniaturization.

[0040] It is understood that the present invention is described by way of some embodiments. Those skilled in the art will appreciate that various changes or equivalent replacements can be made to these features and embodiments without departing from the spirit and scope of the present invention. Additionally, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present invention are within the scope protected by the present invention.

Claims

1. A MEMS chip packaging process for an acoustic device, characterized in that: The following steps are involved: Substrate etching: An electrode is provided on the substrate, and a diaphragm is provided on the electrode. A back cavity is formed by etching from the middle of the surface of the substrate away from the electrode to expose the electrode. The back cavity is located directly below the electrode. At the same time, the etching penetrates other parts of the substrate to form circuit holes to expose the electrodes; Circuit plating: Electroplating metal fills the circuit hole to form a circuit. One end of the circuit is electrically connected to the electrode, and the other end of the circuit is exposed flush with the substrate surface.

2. The MEMS chip packaging process of the acoustic device according to claim 1, characterized in that: In the substrate etching step, the material of the substrate is selected from one or more of flexible materials, glass, and semiconductor materials.

3. The MEMS chip packaging process of the acoustic device according to claim 1, characterized in that: In the substrate etching step, the substrate is covered with an electrode, which is a porous structure.

4. The MEMS chip packaging process of the acoustic device according to claim 3, characterized in that: In the substrate etching step, a diaphragm is covered on the electrode, and the distance between the diaphragm and the electrode is 1-5 μm.

5. The MEMS chip packaging process of the acoustic device according to claim 4, characterized in that: In the substrate etching step, the material of the diaphragm is selected from one or more of polysilicon, silicon nitride or metal.

6. The MEMS chip packaging process of the acoustic device according to claim 1, characterized in that: In the circuit electroplating step, electroplating solder feet are extended on the surface of the substrate where the circuit is exposed, and the solder feet are electrically connected to the circuit.

7. The MEMS chip packaging process for an acoustic device according to claim 1, characterized in that: In the circuit electroplating step, the diaphragm generates mechanical vibration, causing the electrical value to change, and is transmitted through the electrode, the circuit, and the solder pin in sequence.

8. A MEMS chip packaging structure of an acoustic device, comprising a substrate, characterized in that: Also includes: An electrode and a diaphragm, wherein the electrode is arranged above the substrate, and the diaphragm is arranged above the electrode; A back cavity is formed by etching through the middle of the surface of the substrate away from the electrode to expose the electrode, and the back cavity is located directly below the diaphragm and the electrode; A circuit is formed by etching through other parts of the substrate to form a circuit hole, and metal is electroplated in the circuit hole to form a circuit. One end of the circuit is electrically connected to the electrode, and the other end of the circuit is exposed flush with the substrate surface.

9. The MEMS chip packaging structure of the acoustic device according to claim 8, characterized in that: The material of the substrate is selected from one or more of flexible materials, glass, and semiconductor materials.

10. The MEMS chip packaging structure of the acoustic device according to claim 8, characterized in that: The substrate is covered with electrodes, which are porous structures.

11. The MEMS chip packaging structure of the acoustic device according to claim 9, characterized in that: The electrode is covered with a diaphragm, and the distance between the diaphragm and the electrode is 1-5 μm.

12. The MEMS chip packaging structure of the acoustic device according to claim 10, characterized in that: The material of the diaphragm is selected from one or more of polysilicon, silicon nitride or metal.

13. The MEMS chip packaging structure of the acoustic device according to claim 8, characterized in that: Electroplated solder feet are extended on the surface of the substrate where the circuit is exposed, and the solder feet are electrically connected to the circuit.

14. The MEMS chip packaging structure of the acoustic device according to claim 8, characterized in that: The diaphragm generates mechanical vibration, causing electrical value changes, which are transmitted through electrodes, circuits, and solder pins in sequence.

15. An acoustic device, characterized in that: A MEMS chip packaging structure comprising the acoustic device according to claim 8.

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