Shenzhen Geyi Technology Co., Ltd. , https://www.gy-printer.cn
Description
The invention relates to a MEMS air pressure sensor technology in a microelectromechanical system, in particular to a high precision silicon micro resonant air pressure sensor based on an SOI process.
Background of the invention
Micro-Electro-Mechanical Systems (MEMS) is a mature technology that integrates a variety of micro-machining technologies and utilizes semiconductor technology. MEMS devices can be produced in large quantities and at low cost. In addition, MEMS devices generally have the characteristics of small size and good stability, and are widely used in many fields such as aerospace and automobile manufacturing.
The output detection signal of the resonant air pressure sensor is directly converted from the vibration frequency signal of the resonator. Compared with the amplitude signals (mainly voltage amplitude) of the capacitive, resistive and piezoelectric outputs, the frequency signal has a higher frequency signal. Stability and anti-interference ability.
The sensitive structure of the existing silicon microresonant air pressure sensor is generally designed to be composed of a resonator and a gas pressure sensitive membrane. The measured pressure is converted into a strain of the diaphragm by the air pressure sensitive membrane, and the strain of the diaphragm causes the resonant beam to be subjected to axial stress. , thereby changing its stiffness characteristics, which in turn causes the frequency of the resonant beam to change, and the magnitude of the air pressure is obtained by measuring the frequency of the resonant beam.
To achieve barometric pressure measurement, a vacuum reference cavity is typically formed on the side of the air pressure sensitive membrane. To improve performance, the resonator also needs to be placed in a vacuum environment. Yokogawa Electric Corporation of Japan uses a method of on-chip vacuum sealing (refer to the patent application "Vibration type pressure sensor", patent application number: US2006/0010981 A1) to realize vacuum sealing of the resonator. The patent application with the application number CN201010247579 .3 refers to the method of vacuum packaging of the metal shell, which simultaneously realizes the vacuum sealing of the resonator and the establishment of the vacuum reference cavity by a single vacuum packaging, but the single chip packaging method has low production efficiency. The product cost is high. Patent application CN201010218423 .2 refers to a wafer-level package using an intermediate layer bonding technique. A substrate fabricated by a semiconductor process and a lower cover substrate are bonded and bonded by a resin material to form a vacuum reference cavity to achieve a wafer level. Package.
However, the method mentioned in CN201010218423 .2 will not place four resonators in the vacuum reference cavity, exposing the resonator to the atmosphere, greatly reducing the quality factor of the resonator. In addition, the organic materials used in the intermediate layer bonding technology introduce large stresses, which affect the output stability of the air pressure sensor.
Summary of the invention
In order to solve the above problems in the prior art, the present invention provides a high-precision silicon micro-resonant air pressure sensor based on an SOI process, comprising: a sensor chip (1) including an SOI silicon wafer (9) and a borosilicate glass cover sheet (10) having two H-type resonators (11), a support anchor point (12) and a gas pressure sensitive film (13); a type resonator (11) is fixedly supported on the air pressure sensitive film (13) by the support anchor point (12); the borosilicate glass cover sheet (10) and the SOI silicon sheet (9) pass an anode bond The grounding manner is tightly integrated to enclose a vacuum reference cavity (16) such that the two H-type resonators (11) are sealed in the vacuum reference cavity. 
The figure is a schematic cross-sectional view of the sensor chip proposed by the present invention.
Among them, in order to further reduce the influence of thermal stress on the device, the stress isolation layer 2 only fixes one corner of the sensor chip 1. The sensor chip 1, the stress isolation layer 2 and the metal stem 3 can be bonded together by epoxy glue to fix and support the chip. In order to protect the chip and the lead of the gold ball ball bonding, the cap 4 with the magnet is placed on the metal tube seat, and the lower end thereof is fixed to the periphery of the metal tube seat through the epoxy glue.
The scheme of the invention adopts the design of two resonators, which is beneficial to adjust parameters such as the length of the resonator and the position of the fixing point; and the invention directly uses low-resistance silicon to conduct electricity, and the trench and SOI silicon obtained by deep etching are obtained. The insulating layer in the sheet is used to insulate different current paths; the invention improves the quality factor of the sensor by encapsulating the resonator in a vacuum; the invention also uses silicon-glass anodic bonding to complete the vacuum packaging, which effectively improves the efficiency. Production efficiency and reduced thermal stress.
Compared with the prior art, the invention has the significant advantages of using the anodic bonding method to realize the wafer-level vacuum packaging, which can improve the production efficiency and reduce the cost while reducing the stress and improving the output stability of the sensor, thereby reducing the chip package. Cost; the quality of the resonator enclosed in the vacuum sealed cavity is higher, the output is more stable, and the air pressure sensor can obtain higher resolution; the sensor chip can directly lead the wire by gold ball bonding, and solve the wafer-level package lead Difficult problem; using electromagnetic excitation and electromagnetic detection methods, effectively compensating the energy consumption of the resonator and improving the sensor quality factor; the sensor processing process is simple, the yield is high, and it is suitable for mass production.
High precision silicon micro-resonant air pressure sensor
There is no limit to creativity, and the instrument is invented. Today we introduce a national invention patent for authorization - a high-precision silicon micro-resonance air pressure sensor based on SOI technology. The patent was applied by the Institute of Electronics of the Chinese Academy of Sciences and was granted an authorization announcement on March 8, 2017.