Micro machine differential capacitance accelerometer with symmetrical structure

Abstract

The invention relates to a micro machine differential capacitance accelerometer with a symmetrical structure, which is connected with a movable silicon structure component through an anchoring area along the upper direction and the lower direction. Elastic supporting beams of the silicon structure component are divided into an upper layer and a lower layer and distributed between a movable mass block and a fixedly supported frame as well as connected with the movable mass block and the fixedly supported frame; and the round angle transition is adopted at joints of the movable mass block and the fixedly supported frame as well as the beams; both the upper surface and the lower surface of the movable mass block are provided with gas flow guide grooves; and an electrode cover plate can be made of a silicon material. The gas flow guide grooves distributed on both the upper surface and the lower surface of the mass block are beneficial to regulating the squeeze-film damping effect of the accelerometer so as to structurally improve the dynamic characteristic of the surface separated capacitance detection accelerometer. A plurality of the elastic supporting beams of the accelerometer aremade of single crystal silicon materials with a single doping concentration, thereby eliminating thermal inconsistency stress caused by adopting different materials and the thermal inconsistency stress caused by different single crystal silicon doping concentrations.

Description

technical field [0001] The invention relates to a MEMS (micromachine, also known as microelectromechanical system) differential capacitive accelerometer capable of high-precision detection of uniaxial acceleration, in particular to a micromechanical differential capacitive accelerometer with a symmetrical structure, belonging to capacitive accelerometers technology field. Background technique [0002] Silicon single crystal material has good electrical properties and is the basic material of microelectronics technology. In addition, silicon also has good mechanical properties, its fracture strength is three times that of stainless steel, its Knoop hardness is higher than that of stainless steel, and its elasticity is comparable to that of stainless steel. MEMS technology is just a kind of microelectronic three-dimensional processing technology developed after people fully realize the outstanding electromechanical properties of single crystal silicon materials. Microsensors...

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Problems solved by technology

Eric Peeters et al. used ordinary single crystal silicon wafers to control the thickness of the beam structure through concentrated boron diffusion and self-stop corrosion, which introduced a large stress, which would cause the temperature characteristics of the accelerometer to decline; in addition, the accelerometer’s The process has a fragile silicon substrate bonding process, which affects the yield of this accelerometer

[0006] In 2000, the Najafi research group of the University of Michigan made an all-silicon high-precision capacitive accelerometer. This accelerometer adopts a double-layer cantilever beam design, has a fully symmetrical structure, and is processed by a single single-crystal silicon wafer. , to achieve micro-g level acceleration detection, but the accelerometer adopts the concentrated boron diffusion self-stop corrosion process, which introduces a large stress, and the accelerometer has a fragile structure and poor practicability

[0007] The series of patents U.S.Pat.No.5484073; U.S.Pat.No.5652384; U.S.Pat.No.5852242; U.S.Pat.No. applied by I / O Sensors in the United States are successful solutions for high-precision micromachined accelerometers, but this solution Using two SOI wafers after deep etching for silicon-silicon bonding has the problems of high bonding risk, low bonding efficiency, and the reduction of sensitive structure symmetry caused by the inhomogeneity of the process results between the wafers during processing. problem, in addition, this scheme is difficult to achieve effective overload protection for non-sensitive axial

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