CN-120102927-B - Comb tooth capacitive Z-axis acceleration sensitive chip with overlapped structure and manufacturing method thereof

CN120102927BCN 120102927 BCN120102927 BCN 120102927BCN-120102927-B

Abstract

The invention discloses a comb-tooth capacitive Z-axis acceleration sensitive chip with an overlapped structure and a manufacturing method thereof, and belongs to the technical field of MEMS sensors. The sensitive chip is formed by overlapping a comb tooth capacitor layer and an elastic beam structure layer, and the comb tooth capacitor layer and the elastic beam structure layer are bonded together through an oxide layer. Besides the advantage of small damping coefficient, the structure has the advantages that the structure in which the comb tooth capacitor and the elastic beam are overlapped does not need to occupy additional chip area, so that miniaturization is facilitated, chip cost can be reduced, the structure in which the comb tooth capacitor and the elastic beam are overlapped avoids the space of the elastic beam for occupying the comb teeth distributed around the mass block during plane placement, the number of the comb teeth is greatly increased, capacitance of the comb tooth structure is effectively increased, and the overlapped structure enables the elastic beam to be symmetrically distributed around the mass block, so that cross coupling influence in X-axis and Y-axis directions is remarkably reduced.

Inventors

ZHU XIWEN
CHUAI RONGYAN
WANG JIANXING
QIAO ZIMING

Assignees

哈尔滨工业大学

Dates

Publication Date: 20260508
Application Date: 20250221

Claims (6)

1. The stacked structure comb tooth capacitance type Z-axis acceleration sensitive chip is characterized by comprising a comb tooth capacitance layer (1) and an elastic beam structure layer (2), wherein the comb tooth capacitance layer (1) and the elastic beam structure layer (2) are bonded to form an integral structure, the integral structure comprises a mass block (3) and a frame (4), the comb tooth capacitance layer (1) is made of n-type or p-type monocrystalline silicon, a first area (5) is distributed on the comb tooth capacitance layer, a fixed comb tooth (6) connected with the frame (4) is made on the first area (5), movable comb teeth (7) connected with the mass block (3) are made on the first area (5), areas (8, 9 and 10) with metal layers are distributed on the comb tooth capacitance layer (1), through holes (11 and 12) communicated with SOI top silicon on the elastic beam structure layer (2) are etched on the areas (9) and (10), an elastic beam (13) is made on the elastic beam structure layer (2), the mass block (3) is connected with the frame (4) through the elastic beam (13), the fixed comb teeth (6) are connected with an acceleration signal through the elastic beam (6) and the movable comb tooth (7) are connected with an acceleration circuit (8) through the movable comb tooth detection circuit, and the acceleration signal is converted into an acceleration signal circuit (8) through the movable comb tooth circuit; elastic beams (13) which are symmetrically distributed are manufactured on the elastic beam structure layer (2); the comb tooth capacitor layer (1) and the elastic beam structure layer (2) are bonded through an oxide layer.
2. The comb-tooth capacitive Z-axis acceleration sensitive chip with the overlapping structure according to claim 1, wherein the first area (5) is a p-type or n-type area.
3. The comb-tooth capacitive type Z-axis acceleration sensitive chip with the overlapped structure according to claim 1 is characterized in that areas (8, 9 and 10) of evaporated metal layers are distributed on the comb-tooth capacitive layer (1).
4. The manufacturing method of the overlapped structure comb tooth capacitance type Z-axis acceleration sensitive chip as claimed in any one of claims 1 to 3 is characterized by comprising the following steps: Manufacturing an elastic beam structure layer (2) by adopting an SOI substrate and a monocrystalline silicon piece A, and manufacturing an elastic beam (13) on top silicon of the SOI substrate by an etching technology; silicon-silicon bonding is carried out on one side of an elastic beam of the SOI substrate through an oxide layer and a monocrystalline silicon piece A, the monocrystalline silicon piece A is thinned to a required thickness after bonding, and then a groove is formed above the elastic beam through an etching technology, so that the elastic beam (13) is exposed; Step three, manufacturing a comb tooth capacitor layer (1) by adopting a monocrystalline silicon piece B, bonding the monocrystalline silicon piece B with one grooved side of an elastic beam structure layer (2) through an oxide layer, and thinning the monocrystalline silicon piece B to a required thickness; Step four, carrying out local doping on the basis of the step three to form a first region (5); thinning the back of the corresponding area of the mass block (3) on the basis of the fourth step, and reserving a proper movement gap for downward displacement of the mass block (3); step six, after the back surface of the step five is thinned, the elastic beam (13) is released through an etching technology; etching the through holes (11, 12) by utilizing a wet etching technology, exposing a monocrystalline silicon layer where the elastic beam (13) is positioned at the through hole, and etching a lead hole (14) on the first area (5); Step eight, evaporating a layer of metal on the structure with the through hole formed in the step seven, etching metal areas (8, 9 and 10), and then enabling the metal layer and a semiconductor below the metal layer to form good ohmic contact through an alloy process; Step nine, on the basis of the step eight, carrying out anode bonding on the back surface of the integral structure and a proper glass sheet; And step ten, manufacturing fixed comb teeth (6) and movable comb teeth (7) on the first area (5) by utilizing an etching technology.
5. The method for manufacturing the comb-tooth capacitive Z-axis acceleration sensitive chip with the overlapped structure according to claim 4, further comprising the step eleven of manufacturing a cover plate by using a monocrystalline silicon wafer C, etching openings for releasing metal layer areas (8 and 9) on the cover plate, etching a thinning area, providing a proper movement gap for upward displacement of a mass block (3), and finally performing BCB bonding on the cover plate and a main structure to finish main process manufacturing.
6. The method for manufacturing the comb-tooth capacitive type Z-axis acceleration sensitive chip with the overlapped structure, which is disclosed in claim 4, is characterized in that in the third step, an n-type or p-type monocrystalline silicon wafer B is adopted to manufacture the comb-tooth capacitive layer (1).

Description

Comb tooth capacitive Z-axis acceleration sensitive chip with overlapped structure and manufacturing method thereof Technical Field The invention relates to a technical method for improving the performance of a capacitive acceleration sensitive chip and a manufacturing method of the sensitive chip, belonging to the sensor technology in the field of micro-electromechanical system (MEMS) systems. The invention provides a sensitive chip design and a manufacturing method thereof for improving the performance of a comb-tooth capacitive acceleration sensitive chip, which can effectively reduce the area of the comb-tooth capacitive acceleration sensitive chip and has the advantages of high output linearity and small cross coupling. Background Microelectromechanical Systems (MEMS) are leading-edge research fields involving a number of discipline techniques, such as electronics, mechanics, physics, biomedicine, etc. The MEMS sensor is widely applied to the fields of aerospace, medical equipment, automobile electronics, intelligent terminals and the like by virtue of the advantages of miniaturization, low cost, low power consumption and easy intellectualization of the MEMS sensor, which are compatible with an integrated technology. MEMS sensors can be classified into various types including acceleration sensors, temperature sensors, pressure sensors, sound sensors, humidity sensors, and gas sensors, among others. The acceleration sensor may be divided into various types of accelerometers, such as capacitive, resonant, piezoelectric, piezoresistive, and optical accelerometers, according to different detection modes. Capacitive micro-acceleration sensors are one of the most common micro-acceleration sensors, and the principle thereof is to reflect the magnitude of acceleration by detecting the amount of capacitance change caused by the motion caused by inertial force. The capacitive acceleration sensor has the characteristics of high sensitivity and measurement precision, good stability, small temperature drift, low power consumption and the like, and is widely applied to the commercial fields of automobile electronics, consumer electronics and the like. Particularly, the method is highly valued in the fields of inertial measurement, national defense, military industry and the like. In the current market, the MEMS capacitive acceleration sensor can be roughly divided into a sandwich type capacitive acceleration sensor, a torsional pendulum type capacitive acceleration sensor and a comb type capacitive acceleration sensor according to different structural forms. The sandwich type capacitive acceleration sensor generally has the advantages of complex processing technology, higher sensitivity, better detection precision, better linearity, small influence by temperature and certain overload resistance. The torsional pendulum type capacitive acceleration sensor has a simple structure and good integration, multi-axis detection can be realized, the detection sensitivity is weaker than that of a sandwich type capacitive acceleration sensor, and meanwhile, the torsional pendulum type capacitive acceleration sensor is an asymmetric sensitive mass block, so that the sensitive structure is not beneficial to resisting regional stress formed by larger impact. Compared with the first two structures, the comb-tooth capacitive acceleration sensor can well eliminate the coupling between different axial accelerations based on the characteristics of the comb-tooth structures, and has lower cross coupling. Comb-tooth acceleration sensors generally have two structures, namely a surface structure and a bulk silicon structure. The surface structure is a structure manufactured by a surface MEMS processing technology and comprises movable comb teeth positioned on the mass block and fixed comb teeth positioned on the periphery. The structure which is required to be manufactured by the bulk silicon MEMS processing technology belongs to the bulk silicon structure. The surface structure and the IC process have better compatibility, but the Z-axis sensitive acceleration sensor is difficult to manufacture by using the surface structure and the IC process, and the cross coupling is generally larger. The surface structure also has a weakness that is measured by the change in capacitance of the teeth caused by the change in the gap between the teeth, which is more damped by the air. Vacuum packaging is generally required to reduce this damping. The comb-tooth type acceleration sensor with the bulk silicon structure has the advantages that gaps among the comb teeth are kept unchanged during measurement, the measurement is realized through the change of capacitance of the comb teeth caused by the relative position sliding between the fixed comb teeth and the movable comb teeth, the air damping is small, the thermal mechanical noise is low, and the device can be packaged in a vacuum mode. However, the elasticity Liang Jiaochang of the bulk silicon structur