A micro-electromechanical system structure and manufacturing method thereof

Abstract

The present invention provides a micro-electromechanical system structure and a manufacturing method thereof, wherein the micro-electromechanical system structure comprises: a first semiconductor wafer, which is provided with a first cavity, a CMOS circuit and a protective layer, wherein the first cavity is provided on the front of the first semiconductor wafer, the CMOS circuit is provided in the first semiconductor wafer and is located below the first cavity, and the protective layer is located at the bottom of the first cavity and is located above the CMOS circuit; a second semiconductor wafer, which is a micro-electromechanical system unit of a sensor, and comprises a fixed structure, a movable structure and a groove, the second semiconductor wafer is bonded to the front of the first semiconductor wafer, and the first cavity is opposite to the movable structure; a third semiconductor wafer, which is bonded to the back of the second semiconductor wafer, and a second cavity is provided at a relative position between the front of the third semiconductor wafer and the movable structure of the second semiconductor wafer. Compared with the prior art, the present invention can effectively prevent or reduce the generation of PID to protect the CMOS circuit.

Description

[Technical field]

[0001] The present invention relates to the technical field of integrated sensors, and in particular to a micro-electromechanical system structure having a protective effect on a CMOS (Complementary Metal Oxide Semiconductor) circuit and a manufacturing method thereof. [Background technology]

[0002] Micro-electromechanical systems have broad application prospects in the national economy and military systems. The main civilian fields are electronics, medicine, industry, automobiles and aerospace systems. In actual applications, CMOS and MEMS often exist at the same time. Among them, the MEMS (Micro-Electro-Mechanical System) structure includes a fixed structure and a movable structure. In the process of etching the MEMS structure to form a fixed structure and a movable structure, the CMOS circuit located at the bottom layer of the MEMS will be exposed to the atmosphere of plasma etching. If the CMOS layer is not protected, the induced plasma will cause permanent plasma induced damage PID (Plasma Induced Damage) to the CMOS circuit, which will cause irreversible damage to the functions of the circuit and the device.

[0003] Therefore, it is necessary to propose a new technical solution to solve the above problems. [Summary of the invention]

[0004] One of the purposes of the present invention is to provide a micro-electromechanical system structure and a manufacturing method thereof, which can effectively prevent or reduce the generation of PID to protect CMOS circuits.

[0005] According to one aspect of the present invention, the present invention provides a micro-electromechanical system structure, which includes:

[0006] A first semiconductor wafer is provided with a first cavity, a CMOS circuit and a protective layer, wherein the first cavity is provided on the front side of the first semiconductor wafer, the CMOS circuit is provided in the first semiconductor wafer and is located below the first cavity, and the protective layer is located at the bottom of the first cavity and is located above the CMOS circuit; a second semiconductor wafer is a micro-electromechanical system unit of a sensor, and comprises a fixed structure located at the edge of a chip, a movable structure located in the middle of the chip, and a groove located in the movable structure region and penetrating the chip, the second semiconductor wafer is bonded to the front side of the first semiconductor wafer, The front side of the second semiconductor wafer is opposite to the front side of the first semiconductor wafer, and the first cavity is arranged at the relative position between the front side of the first semiconductor wafer and the movable structure of the second semiconductor wafer; a third semiconductor wafer is bonded to the back side of the second semiconductor wafer, the front side of the third semiconductor wafer is opposite to the back side of the second semiconductor wafer, and the second cavity is arranged at the relative position between the front side of the third semiconductor wafer and the movable structure of the second semiconductor wafer, wherein the first cavity and the second cavity are opposite to form a cavity A, and the movable structure of the second semiconductor wafer is suspended in the cavity A.

[0007] According to another aspect of the present invention, the present invention provides a method for manufacturing a micro-electromechanical system structure, which includes: providing a first semiconductor wafer, which is provided with a first cavity and a CMOS circuit, the first cavity is provided on the front side of the first semiconductor wafer, and the CMOS circuit is provided in the first semiconductor wafer and is located below the first cavity; providing a second semiconductor wafer, the second semiconductor wafer is a micro-electromechanical system unit of a sensor; providing a third semiconductor wafer, the front side of the third semiconductor wafer is provided with a second cavity; forming a protective layer at the bottom of the first cavity of the first semiconductor wafer, the protective layer is opposite to the CMOS circuit and is located above the CMOS circuit; S circuit; bonding the first semiconductor wafer provided with the protective layer to the front side of the second semiconductor wafer, after bonding, the front side of the second semiconductor wafer is opposite to the front side of the first semiconductor wafer; etching the second semiconductor wafer bonded to the first semiconductor wafer to form a fixed structure, a movable structure and a groove of the micro-electromechanical system unit of the sensor; bonding a third semiconductor wafer to the back side of the etched second semiconductor wafer, after bonding, the front side of the third semiconductor wafer is opposite to the back side of the second semiconductor wafer, and the second cavity on the front side of the third semiconductor wafer is opposite to the movable structure of the second semiconductor wafer.

[0008] Compared with the prior art, the present invention adds a conductive protective layer material on the surface of the CMOS circuit and grounds it. On the one hand, it can effectively prevent or reduce the generation of PID and protect the underlying CMOS circuit. At the same time, it can also prevent impurities generated during the etching process from remaining on the bottom and sides of the MEMS structure layer, causing damage to the MEMS structure or failure of the device.

Brief Description of the Drawings

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0010] Figure 1 is a schematic longitudinal cross-sectional view of a micro-electromechanical system structure in one embodiment of the present invention;

[0011] Figure 2 A schematic flow chart of a method for manufacturing a micro-electromechanical system structure in one embodiment of the present invention;

[0012] Figure 3-Figure 10 In one embodiment of the present invention Figure 2 The longitudinal cross-sectional views corresponding to the steps shown. [Specific implementation method]

[0013] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments. Unless otherwise specified, the words "connected", "connected", and "connected" herein that indicate electrical connection all refer to direct or indirect electrical connection.

[0015] Please refer to Figure 1 , which is a schematic longitudinal cross-sectional view of a micro-electromechanical system structure in one embodiment of the present invention. Figure 1The MEMS structure shown includes a first semiconductor wafer 1, a second semiconductor wafer 3 and a third semiconductor wafer 4. After semiconductor wafer-level bonding, a semiconductor wafer cutting step is performed to form a plurality of mutually independent chip structures, i.e., independent chips. The independent chips then continue to be packaged. From the perspective of the semiconductor wafer before cutting, i.e., from the perspective of the semiconductor wafer level, the first semiconductor wafer, the second semiconductor wafer and the third semiconductor wafer are three independent semiconductor wafers, and from the perspective of the semiconductor wafer after cutting, i.e., from the perspective of the chip level, the first semiconductor wafer, the second semiconductor wafer and the third semiconductor wafer can be understood as wafers of each semiconductor wafer.

[0016] The first semiconductor wafer 1 is provided with a first cavity 102, a CMOS (Complementary Metal Oxide Semiconductor) circuit 101 and a protective layer 2. The first cavity 102 is provided on the front of the first semiconductor wafer 1; the CMOS circuit 101 is provided in the first semiconductor wafer 1 and is located below the first cavity 102; the protective layer 2 is located at the bottom of the first cavity 102 and is opposite to the CMOS circuit 101 (or is located above the CMOS circuit 101), and the protective layer 2 is grounded. The material of the protective layer 2 is a conductor, and the material is not limited, and can be metal, polysilicon and other materials. Figure 1 In the specific embodiment shown, a groove 103 is provided at the bottom of the first cavity 102 of the first semiconductor wafer 1 , and the protection layer 2 is filled in the groove 103 .

[0017] The second semiconductor wafer 3 is a micro-electromechanical system unit of the sensor, which includes a fixed structure 301 located at the edge of the chip (or wafer), a movable structure 302 located in the middle of the chip, and a groove 303 located in the movable structure 302 area and running through the chip (or wafer). The second semiconductor wafer 3 is bonded to the front side of the first semiconductor wafer 1, the front side of the second semiconductor wafer 3 is opposite to (or adjacent to) the front side of the first semiconductor wafer 1, and a pre-processed first cavity 102 is provided at the relative position between the front side of the first semiconductor wafer 1 and the movable structure 302 of the second semiconductor wafer 3 (or the first cavity 102 on the front side of the first semiconductor wafer 1 is opposite to the movable structure 302 of the second semiconductor wafer 3).

[0018] The third semiconductor wafer 4 is a packaging cover (Cap) of the sensor, which is bonded to the back side of the second semiconductor wafer 3. The front side of the third semiconductor wafer 4 is opposite to (or adjacent to) the back side of the second semiconductor wafer 3, and a pre-processed second cavity 401 is provided at the relative position between the front side of the third semiconductor wafer 4 and the movable structure 302 of the second semiconductor wafer 3.

[0019] That is, the first semiconductor wafer 1 and the third semiconductor wafer 4 are in contact with the front and back surfaces of the second semiconductor wafer 3, respectively. After bonding, the first cavity 102 of the first semiconductor wafer 1 and the second cavity 401 of the third semiconductor wafer 4 are opposite to form a cavity A, and the movable structure 302 of the second semiconductor wafer 3 is suspended in the cavity A. In one embodiment, the cavity A is a vacuum or a positive pressure gas containing a predetermined pressure.

[0020] In summary, the micro-electromechanical system structure in the present invention is a CMOS-MEMS structure, wherein the number and type of MEMS are not limited, and the MEMS may be an accelerometer, a microphone, a pressure sensor, a gyroscope, a humidity sensor, etc., and their integrated products.

[0021] Please refer to Figure 2 As shown, it is a flow chart of a method for manufacturing a micro-electromechanical system structure in one embodiment of the present invention; please refer to Figure 3-Figure 10 As shown, it is an embodiment of the present invention Figure 2 The longitudinal cross-sectional views corresponding to the steps shown. Figure 2 The manufacturing method of the MEMS structure shown includes the following steps.

[0022] Step 210: Figure 3 As shown, a first semiconductor wafer 1 is provided, on which a first cavity 102 and a CMOS (Complementary Metal Oxide Semiconductor) circuit 101 are disposed. The first cavity 102 is disposed on the front side of the first semiconductor wafer 1; the CMOS circuit 101 is disposed in the first semiconductor wafer 1 and is located below the first cavity 102.

[0023] Step 220: Figure 4 As shown, a second semiconductor wafer 3 is provided, and the second semiconductor wafer 3 is a micro-electromechanical system unit of the sensor.

[0024] Step 230: Figure 5 As shown, a third semiconductor wafer 4 is provided, and a second cavity 401 is disposed on the front side of the third semiconductor wafer 4 .

[0025] Step 240: Figure 6 As shown, the bottom of the first cavity 102 of the first semiconductor wafer 1 is etched to form a trench 103 .

[0026] Step 250: Figure 7 As shown, a conductive material is deposited at the position of the groove 103 to form a protective layer 2, that is, the protective layer 2 is filled in the groove 103. Among them, the function of step 240 and step 250 is to form the protective layer 2 at the bottom of the first cavity 102, the protective layer 2 is opposite to the CMOS circuit 101 (or is located above the CMOS circuit 101), and the protective layer 2 is grounded. The material of the protective layer 2 is a conductor, and the material is not limited, and can be a material such as metal and polysilicon.

[0027] Step 260: Figure 8 As shown, the first semiconductor wafer 1 provided with the protection layer 2 is bonded to the front side of the second semiconductor wafer 3 . After bonding, the front side of the second semiconductor wafer 3 is opposite to (or adjacent to) the front side of the first semiconductor wafer 1 .

[0028] Step 270: Fig. 9 As shown, the second semiconductor wafer 3 bonded to the first semiconductor wafer 1 is etched to form a fixed structure 301, a movable structure 302 and a groove 303 of the micro-electromechanical system unit of the sensor, wherein the fixed structure 301 is located at the edge of the chip (or wafer), the movable structure 302 is located in the middle of the chip, and the groove 303 is located in the movable structure 302 area and passes through the chip (or wafer). The first cavity 102 on the front side of the first semiconductor wafer 1 is opposite to the movable structure 302 of the second semiconductor wafer 3.

[0029] Step 280: Fig.10 As shown, the third semiconductor wafer 4 is bonded to the back side of the etched second semiconductor wafer 3. After bonding, the front side of the third semiconductor wafer 4 is opposite to (or adjacent to) the back side of the second semiconductor wafer 3, and the second cavity 401 on the front side of the third semiconductor wafer 4 is opposite to the movable structure 302 of the second semiconductor wafer 3.

[0030] That is, the first semiconductor wafer 1 and the third semiconductor wafer 4 are in contact with the front and back surfaces of the second semiconductor wafer 3, respectively. After bonding, the first cavity 102 of the first semiconductor wafer 1 and the second cavity 401 of the third semiconductor wafer 4 are opposite to form a cavity A, and the movable structure 302 of the second semiconductor wafer 3 is suspended in the cavity A. In one embodiment, the cavity A is a vacuum or a positive pressure gas containing a predetermined pressure.

[0031] In summary, the micro-electromechanical system structure manufactured by the manufacturing method of the present invention is a CMOS-MEMS structure, wherein the number and type of MEMS are not limited, and the MEMS can be an accelerometer, a microphone, a pressure sensor, a gyroscope, a humidity sensor, etc. and their integrated products.

[0032] In summary, the present invention adds a conductive protective layer material on the surface of the CMOS circuit and grounds it. On the one hand, it can effectively prevent or reduce the generation of PID and protect the underlying CMOS circuit. At the same time, it can also prevent impurities generated during the etching process from remaining on the bottom and sides of the MEMS structure layer, causing damage to the MEMS structure or failure of the device.

[0033] In the present invention, words such as “connect”, “connected”, “connected”, “connected”, etc. indicating electrical connection, if not otherwise specified, indicate direct or indirect electrical connection.

[0034] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the content disclosed in the present invention should be included in the protection scope recorded in the claims.

Claims

1. A micro-electromechanical system structure, characterized in that: It includes: A first semiconductor wafer (1), provided with a first cavity (102), a CMOS circuit (101) and a protective layer (2), wherein the first cavity (102) is provided on the front side of the first semiconductor wafer (1), the CMOS circuit (101) is provided in the first semiconductor wafer (1) and is located below the first cavity (102), and the protective layer (2) is located at the bottom of the first cavity (102) and above the CMOS circuit (101); A second semiconductor wafer (3), which is a micro-electromechanical system unit of a sensor, comprising a fixed structure (301) located at the edge of a chip, a movable structure (302) located in the middle of the chip, and a groove (303) located in the region of the movable structure (302) and penetrating the chip, the second semiconductor wafer (3) being bonded to the front side of the first semiconductor wafer (1), the front side of the second semiconductor wafer (3) being opposite to the front side of the first semiconductor wafer (1), and the first cavity (102) being arranged at a relative position between the front side of the first semiconductor wafer (1) and the movable structure (302) of the second semiconductor wafer (3); A third semiconductor wafer (4) is bonded to the back side of the second semiconductor wafer (3); the front side of the third semiconductor wafer (4) is opposite to the back side of the second semiconductor wafer (3); and a second cavity (401) is provided at a position relative to the front side of the third semiconductor wafer (4) and the movable structure (302) of the second semiconductor wafer (3); wherein the first cavity (102) and the second cavity (401) are opposite to each other to form a cavity A, and the movable structure (302) of the second semiconductor wafer (3) is suspended in the cavity A.

2. The micro-electromechanical system structure according to claim 1, characterized in that: The material of the protective layer (2) is a conductor; The protective layer (2) is grounded.

3. The micro-electromechanical system structure according to claim 1, characterized in that: A groove (103) is provided at the bottom of the first cavity (102) of the first semiconductor wafer (1), and the protective layer (2) is filled in the groove (103).

4. The micro-electromechanical system structure according to claim 1, characterized in that: The micro-electromechanical system structure is an accelerometer, a microphone, a pressure sensor, a gyroscope or a humidity sensor; The cavity A is filled with vacuum or positive pressure gas of a predetermined pressure.

5. A micro-electromechanical system structure and a method for manufacturing the same, characterized in that: It includes: A first semiconductor wafer (1) is provided, wherein the first cavity (102) and a CMOS circuit (101) are provided, wherein the first cavity (102) is provided on the front side of the first semiconductor wafer (1), and the CMOS circuit (101) is provided in the first semiconductor wafer (1) and is located below the first cavity (102); Providing a second semiconductor wafer (3), wherein the second semiconductor wafer (3) is a micro-electromechanical system unit of a sensor; Providing a third semiconductor wafer (4), wherein a second cavity (401) is arranged on the front side of the third semiconductor wafer (4); A protective layer (2) is formed at the bottom of the first cavity (102) of the first semiconductor wafer (1), wherein the protective layer (2) is opposite to the CMOS circuit (101) and is located above the CMOS circuit (101); The first semiconductor wafer (1) provided with the protective layer (2) is bonded to the front side of the second semiconductor wafer (3), and after bonding, the front side of the second semiconductor wafer (3) is opposite to the front side of the first semiconductor wafer (1); Etching the second semiconductor wafer (3) bonded to the first semiconductor wafer (1) to form a fixed structure (301), a movable structure (302) and a groove (303) of a micro-electromechanical system unit of the sensor; The third semiconductor wafer (4) is bonded to the back side of the etched second semiconductor wafer (3); after bonding, the front side of the third semiconductor wafer (4) is opposite to the back side of the second semiconductor wafer (3), and the second cavity (401) on the front side of the third semiconductor wafer (4) is opposite to the movable structure (302) of the second semiconductor wafer (3).

6. The micro-electromechanical system structure and the method for manufacturing the same according to claim 5, characterized in that: Forming a protective layer (2) at the bottom of the first cavity (102) of the first semiconductor wafer (1) comprises: Etching the bottom of the first cavity (102) of the first semiconductor wafer (1) to form a groove (103); A conductive material is deposited at the position of the groove (103) to form the protective layer (2).

7. The micro-electromechanical system structure and the manufacturing method thereof according to claim 5, characterized in that: The fixed structure (301) is located at the edge of the chip, the movable structure (302) is located in the middle of the chip, and the groove (303) is located in the region of the movable structure (302) and runs through the chip; The first cavity (102) on the front side of the first semiconductor wafer (1) is opposite to the movable structure (302) of the second semiconductor wafer (3); The first cavity (102) and the second cavity (401) are opposed to each other to form a cavity A, and the movable structure (302) of the second semiconductor wafer (3) is suspended in the cavity A.

8. The micro-electromechanical system structure according to claim 5, characterized in that: The material of the protective layer (2) is a conductor; The protective layer (2) is grounded.

9. The micro-electromechanical system structure according to claim 5, characterized in that: The micro-electromechanical system structure is an accelerometer, a microphone, a pressure sensor, a gyroscope or a humidity sensor; The cavity A is filled with vacuum or positive pressure gas of a predetermined pressure.

Images