Processing method of differential type high-precision accelerometer

Abstract

The invention discloses a processing method of a differential type high-precision accelerometer. The accelerometer comprises an upper electrode cover plate, a movable silicon structural assembly with a beam-mass block structure and a lower electrode cover plate which are sequentially connected from top to bottom. The method comprises the following steps of: processing the upper electrode plate and the lower electrode plate by using a glass sheet or a monocrystalline silicon wafer as a substrate; processing the movable silicon structural assembly with the beam-mass block structure by using a double-device-layer SOI (Silicon-On-Insulator) monocrystalline silicon wafer as a substrate; and connecting the upper electrode plate and the lower electrode plate which are processed by using the substrates with the movable silicon structural assembly based on a bonding mode. In the invention, only one monocrystalline silicon wafer is adopted to process the movable silicon structural assembly, thereby avoiding the condition that a frequently used high-temperature silicon-silicon bonding process is used for preparing the movable silicon structural assembly, reducing the process difficulty, lowering the highest process temperature and eliminating bonding stress problems introduced by silicon-silicon bonding; and moreover, the beam-mass block structure has generality.

Description

technical field [0001] The invention relates to the field of microelectronic machining, in particular to a processing method for a differential high-precision accelerometer. Background technique [0002] High-sensitivity and low-noise micro-accelerometers are widely used in inertial navigation, geological monitoring, space microgravity measurement and other fields. Due to the use of silicon micromachining technology, MEMS accelerometers have the advantages of low cost, small size, and easy batch self-manufacturing. They have already occupied a dominant position in the field of low-precision and medium-precision accelerometer applications. However, with the reduction of MEMS acceleration volume, problems such as thermal noise, stress, and film damping that are not obvious in traditional accelerometers become significant due to size effects. [0003] In order to improve the signal-to-noise ratio of the MEMS accelerometer, that is, to improve the detection sensitivity, domesti...

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Problems solved by technology

However, in terms of processing 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, resulting in a decrease in the temperature characteristics of the accelerometer; in addition, The processing of this accelerometer has a bonding operation of fragile silicon wafers, which affects the yield of this accelerometer

[0005] In 2000, the Najafi research group of the University of Michigan used a single monocrystalline silicon wafer to make an all-silicon high-precision capacitance accelerometer. This accelerometer also uses a double-layer beam structure with a fully symmetrical structure to achieve microg Magnitude of acceleration detection, but this accelerometer adopts the concentrated boron diffusion self-stop corrosion process to make the beam structure, which introduces a large stress; and the structure of the accelerometer is fragile, it is difficult to achieve dicing packaging, and the practicability is poor

However, in this structure, the additional masses are only distributed on one side of the comb structure, so the center of gravity of the beam-mass structure does not coincide with the center of the supporting force of the beam. serious coupling

[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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