Process processing method of out-of-plane capacitive micro-electromechanical accelerometer
By combining dry and wet etching processes, the problems of large thickness, low alignment accuracy, and easy adhesion of structures in out-of-plane accelerometers processed by wet bulk silicon processes have been solved, enabling the manufacturing of miniaturized and high-performance out-of-plane accelerometers, and supporting flip-chip packaging and capacitor gap formation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIAN FLIGHT SELF CONTROL INST OF AVIC
- Filing Date
- 2025-12-27
- Publication Date
- 2026-05-01
AI Technical Summary
Existing wet bulk silicon fabricated out-of-plane accelerometers suffer from problems such as large thickness, low alignment accuracy, and easy adhesion of the structure, which makes it difficult to reduce the size of the accelerometer, limits the measurement range, and results in the scarcity of commercially available high-performance products.
A process combining dry and wet etching is employed. By bonding silicon electrode layers onto the TSV layer, independent silicon electrodes and sealing rings are formed. The capacitor gap is wet-etched on the underside of the cover plate, while the wobbling structure is dry-etched. Finally, the capacitor gap is formed during bonding, avoiding adhesion problems caused by pre-bonding cleaning. The cross-axis coupling error is compensated by the reverse-paired wobbling structure.
It achieves miniaturization, improves alignment accuracy, avoids structural adhesion, supports submicron capacitance gaps and flip-chip packaging, compensates for cross-axis coupling errors, and enhances the performance of out-of-plane accelerometers.
Smart Images
Figure CN121948375A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microelectromechanical accelerometers, and specifically relates to a manufacturing method for an out-of-plane capacitive microelectromechanical accelerometer. Background Technology
[0002] Capacitive microelectromechanical accelerometers (MEMS) offer advantages such as small size, low power consumption, and good stability. They are commonly used for acceleration, vibration, and tilt measurement and are widely applied in medical, industrial, and military fields. MEMS accelerometers are categorized by their sensing axis into in-plane axial (x, y axes) and out-of-plane axial (z axis) types. After years of development and iteration, the technical solutions for in-plane axial accelerometers have largely reached a consensus in the industry, generally employing a comb-tooth structure design and dry bulk silicon processing. While out-of-plane accelerometers have a longer history, an optimal solution has yet to be found.
[0003] Early out-of-plane accelerometers were generally fabricated using a wet bulk silicon process. Taking advantage of the anisotropy of KOH solution etching single-crystal silicon, capacitor gaps, flexible ribs, and mass blocks were etched out, and the capacitor transducer formed between the mass block and the upper and lower cover plates was used to sense out-of-plane acceleration.
[0004] The drawbacks of this type of accelerometer are quite obvious. The characteristics of the wet etching process for single-crystal silicon make it difficult to reduce the chip size, especially when the structural layer is thick. Furthermore, to support the wet etching gap, the structural layer must be strong enough to support the wet etching process, and its thickness is typically no less than 200µm. This limits the accelerometer's range design to the capacitor gap, making it difficult to achieve a large closed-loop range. To achieve a large range, a seesaw structure was proposed, which decouples the sensing capacitor from the oscillation, but this design generally suffers from translational problems. In addition, the wet-etched oscillation structure needs to be fabricated independently and then bonded to the upper and lower cover plates, inevitably leading to low alignment accuracy and easy adhesion issues. To date, commercially available high-performance out-of-plane microelectromechanical accelerometers based on wet etching processes are still rare. Summary of the Invention
[0005] This invention provides a manufacturing method for an out-of-plane capacitive microelectromechanical accelerometer, which solves the problems of large thickness, low alignment accuracy, and easy adhesion of the structure in existing out-of-plane accelerometers manufactured by wet bulk silicon processes.
[0006] This invention provides a manufacturing method for an out-of-plane capacitive microelectromechanical accelerometer (WEFA), the WEFA comprising: a TSV layer 001, a silicon electrode layer 002, a structural layer 003, and a cover plate 004; wherein, the manufacturing method includes: S1. A silicon electrode layer 002 is bonded to the upper surface of the TSV layer 001. The silicon electrode layer 002 is dry etched to obtain an independent silicon electrode and a sealing ring. A bonding dielectric layer is prepared on the upper surface of the silicon electrode layer 002. S2. A structural layer 003 is bonded to the lower surface of the cover plate 004 layer. A capacitor gap is formed by wet etching on the lower surface of the structural layer 003, and then a seesaw structure is formed by dry etching. S3. Align the seesaw structure of structural layer 003 with the silicon electrode, and bond the lower surface of structural layer 003 and the upper surface of bonding dielectric layer to obtain the capacitor gap. S4. Metallize the vias of TSV layer 001 to bring out the electrical signal from the silicon electrode to the lower surface of TSV layer 001.
[0007] Optionally, after S1 and S2, the method further includes: Pretreatment, cleaning, and drying.
[0008] Optionally, prior to S1, the method further includes: The upper surface of the TSV layer 001 is etched to form raised bonding anchors and bonding sealing rings, so that the outer ring of the silicon electrode and the inner ring of the sealing ring are suspended.
[0009] Optionally, the lower surface of the cover plate 004 is provided with multiple stop protrusions.
[0010] Optionally, the cover plate 004 has a through hole that connects to the frame of the structural layer, and the through hole is metallized to achieve the same potential as the frame of the structural layer.
[0011] Optionally, the seesaw structure includes at least one set of seesaw pairs; each set of seesaw pairs includes two seesaws arranged in opposite directions.
[0012] Optionally, if the bonding failure temperature of S3 is lower than the metallization temperature in S4, S4 will be executed before S3.
[0013] Optionally, the size of the silicon electrode is smaller than the size of the symmetrical part of the seesaw structure.
[0014] This invention provides an out-of-plane capacitive microelectromechanical accelerometer (MEMS) capable of z-axis accelerometer detection, offering a solution for the design and manufacture of out-of-plane accelerometers. The third bonding process creates a capacitor gap, avoiding adhesion issues caused by cleaning the wafers before bonding. This invention forms the final capacitor gap, supporting a submicron capacitor gap. The suspended silicon electrode avoids patterning of the bonding dielectric layer, ensuring compatibility with various bonding technologies. The suspended silicon electrode significantly reduces parasitic capacitance. Internal signal leads are led out from the surface, supporting advanced packaging such as flip-chip bonding. This invention proposes a seesaw reverse pair design to compensate for cross-axis coupling errors caused by insufficient perpendicularity of the sidewall tilt angle. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0016] Figure 1 This is a schematic cross-sectional view of the out-of-plane capacitive microelectromechanical accelerometer. Figure 2 This is a schematic diagram of the seesaw structure during actual implementation; Figures 3-7 A brief implementation process of this out-of-plane capacitive microelectromechanical accelerometer; Explanation of reference numerals in the attached figures: 001-TSV layer, 002-Silicon electrode layer, 003-Structural layer, 004-Cover plate, 005-Silicon electrode, 006-Sealing ring, 007-Capacitor gap, 008-Wag structure, 009-TSV hole, 010-Silicon electrode anchor point, 011-Stop protrusion, 012-Cover plate through hole, 013-Wag pair, 014-Symmetrical part of the pendulum, 015-Asymmetrical part of the pendulum, 016-Wag torsion beam fixing anchor point, 017-Torsion beam. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0018] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.
[0019] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.
[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.
[0021] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0022] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.
[0023] like Figure 1-7 As shown, this invention provides a manufacturing method for an out-of-plane capacitive microelectromechanical accelerometer, the out-of-plane capacitive microelectromechanical accelerometer comprising: a TSV layer 001, a silicon electrode layer 002, a structural layer 003, and a cover plate 004; wherein, the manufacturing method includes: S1. A silicon electrode layer 002 is bonded to the upper surface of the TSV layer 001. The silicon electrode layer 002 is dry etched to obtain an independent silicon electrode and a sealing ring. A bonding dielectric layer is prepared on the upper surface of the silicon electrode layer 002. S2. A structural layer 003 is bonded to the lower surface of the cover plate 004 layer. A capacitor gap is formed by wet etching on the lower surface of the structural layer 003, and then a seesaw structure is formed by dry etching. S3. Align the seesaw structure of structural layer 003 with the silicon electrode, and bond the lower surface of structural layer 003 and the upper surface of bonding dielectric layer to obtain the capacitor gap. S4. Metallize the vias of TSV layer 001 to bring out the electrical signal from the silicon electrode to the lower surface of TSV layer 001.
[0024] Optionally, after S1 and S2, the method further includes: Wash and dry.
[0025] Optionally, prior to S1, the method further includes: The upper surface of the TSV layer 001 is etched to form raised bonding anchors and bonding borders, so that the outer ring of the silicon electrode and the inner ring of the sealing ring are suspended.
[0026] Optionally, the lower surface of the cover plate 004 is provided with multiple stop protrusions.
[0027] Optionally, the cover plate 004 has a through hole that connects to the frame of the structural layer, and the through hole is metallized to achieve the same potential as the frame of the structural layer.
[0028] Optionally, the seesaw structure includes at least one set of seesaw pairs; each set of seesaw pairs includes two seesaws arranged in opposite directions.
[0029] Optionally, if the bonding failure temperature of S3 is lower than the metallization temperature in S4, S4 will be executed before S3.
[0030] Optionally, the size of the silicon electrode is smaller than the size of the symmetrical part of the seesaw structure.
[0031] This invention proposes that when applying this structural scheme, the seesaws should be designed in opposite pairs.
[0032] For example, the out-of-plane capacitance microelectromechanical accelerometer structure obtained by the processing method provided by the present invention is as follows: Figure 1 and 2 As shown, it includes: TSV layer 001, silicon electrode layer 002, structural layer 003, and cover plate 004; Among them, the silicon electrode layer 002 is provided with a silicon electrode 005 and a sealing ring 006, the structural layer 003 is provided with a seesaw structure 008, and a capacitor gap 007 is provided between the seesaw structure 008 and the silicon electrode 005. TSV layer 001 is provided with silicon electrode anchor point 010, and TSV hole 009 is provided in silicon electrode anchor point 010; The cover plate 004 is provided with a stop protrusion 011 and a cover plate through hole 012.
[0033] The seesaw structure 008 includes: seesaw pair 013, symmetrical part of the seesaw 014, asymmetrical part of the seesaw 015, fixed anchor point of the seesaw torsion beam 016, and torsion beam 017.
[0034] The working principle of the accelerometer manufactured using this invention is as follows: When subjected to out-of-plane acceleration, the swaying pendulum twists around the vertical beam formed by dry etching, causing it to form a differential detection capacitor with the silicon electrode to generate a differential output. The magnitude of the acceleration can be obtained by detecting the differential output.
[0035] The implementation process of this invention is as follows: 1. The TSV layer 001 is processed by wet etching and dry etching, and surface insulation is performed; 2. Complete the bonding between silicon electrode layer 002 and TSV layer 001 and dry etch out silicon electrode 005; 3. The cover plate 004 and the stop protrusion 011 are etched using wet and dry methods, and the surface is then insulated. 4. Complete the bonding between structural layer 003 and cover plate 004 and dry etch out the seesaw structure 008; 5. Bond the cover plate 004-structural layer 003 and the TSV layer 001-silicon electrode layer 002 together to complete the signal extraction.
[0036] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.
Claims
1. A manufacturing method for an out-of-plane capacitive microelectromechanical accelerometer, characterized in that, The out-of-plane capacitive microelectromechanical accelerometer comprises: a TSV layer (001), a silicon electrode layer (002), a structural layer (003), and a cover plate (004); wherein, the processing method includes: S1. A silicon electrode layer (002) is bonded to the upper surface of the TSV layer (001), and the silicon electrode layer (002) is dry etched to obtain an independent silicon electrode and a sealing ring; a bonding dielectric layer is prepared on the upper surface of the silicon electrode layer (002); S2. A structural layer (003) is bonded to the lower surface of the cover plate (004) layer. A capacitor gap is formed by wet etching on the lower surface of the structural layer (003), and then a seesaw structure is formed by dry etching. S3. Align the seesaw structure of the structural layer (003) with the silicon electrode, and bond the lower surface of the structural layer (003) and the upper surface of the bonding dielectric layer to obtain the capacitor gap. S4. Metallize the vias of the TSV layer (001) to bring out the electrical signal of the silicon electrode to the lower surface of the TSV layer (001).
2. The manufacturing method of the out-of-plane capacitive microelectromechanical accelerometer according to claim 1, characterized in that, Following S1 and S2, the method further includes: Pretreatment, cleaning, and drying.
3. The manufacturing method of the out-of-plane capacitive microelectromechanical accelerometer according to claim 1, characterized in that, Prior to S1, the method further includes: The upper surface of the TSV layer (001) is etched to form raised bonding anchor points (010) and bonding sealing rings, so that the outer ring of the silicon electrode and the inner ring of the sealing ring are suspended.
4. The manufacturing method of the out-of-plane capacitive microelectromechanical accelerometer according to claim 1, characterized in that, Multiple stop protrusions are provided on the lower surface of the cover plate (004).
5. The manufacturing method of the out-of-plane capacitive microelectromechanical accelerometer according to claim 1, characterized in that, The cover plate (004) has a through hole that connects to the frame of the structural layer. The through hole is metallized to achieve the same potential as the frame of the structural layer.
6. The manufacturing method of the out-of-plane capacitive microelectromechanical accelerometer according to claim 1, characterized in that, The seesaw structure includes at least one pair of seesaws; each pair of seesaws includes two seesaws arranged in opposite directions.
7. The manufacturing method of the out-of-plane capacitive microelectromechanical accelerometer according to claim 1, characterized in that, When the bonding failure temperature of S3 is lower than the metallization temperature in S4, S4 will be executed before S3.
8. The manufacturing method of the out-of-plane capacitive microelectromechanical accelerometer according to claim 1, characterized in that, The size of the silicon electrode is smaller than the size of the symmetrical part of the seesaw structure.