A kind of preparation method of mems pressure sensor

Abstract

The invention discloses a preparation method of an MEMS pressure sensor. The preparation method comprises the following steps: using two SOI wafers, etching the top layer silicon of the first SOI wafer to in a buried oxygen layer by using a dry method to prepare an island structure, bonding the top layer silicon of the second SOI wafer and the top layer silicon of the first SOI wafer with the prepared island structure via silicon-silicon, forming a proper window at the substrate of the first SOI wafer with the prepared island structure, corroding to the buried oxygen layer via a KOH solution,removing the buried oxygen layer via a gaseous state HF to form an island structure movement gap and an overload structure, bonding the prepared structure and a double cast silicon wafer via silicon-silicon, thinning the substrate of the second SOI wafer, removing the buried oxygen layer of the second SOI wafer to form a sensitive thin film, manufacturing a piezoresistor and an electrode lead, andfinally preparing the whole MEMS pressure sensor. By adoption of the method, the thickness of the island structure can be accurately controlled, the thickness of the top layer silicon of the first SOI wafer is the thickness of the island structure; and meanwhile, an overload resistance structure is achieved, and the MEMS pressure sensor is suitable for mass production.

Description

technical field [0001] The invention relates to the technical field of micro-mechanical electronics, in particular to a method for preparing a MEMS pressure sensor. Background technique [0002] MEMS silicon pressure sensor is the most important type of sensor in industrial production at present, and is widely used in automobile industry, aerospace industry, military, medical and health and other fields. The piezoresistive pressure sensor is currently the most widely used type of pressure sensor. Using the good mechanical and electrical properties of silicon, the force-sensitive resistor is injected into the sensitive film by diffusion or ion implantation to realize the pressure-sensitive element and conversion circuit. integration. The two most important parameters to measure a pressure sensor are sensitivity and linearity. For the traditional C-type silicon cup structure, to improve the sensitivity of the pressure sensor, the sensitive film must be thinned to increase th...

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Problems solved by technology

In addition, in order to ensure the frequency response output of the pressure test and avoid the interference of environmental factors on the test, the height of the silicon island is strictly controlled, generally less than 100 μm, and the island film structure is mostly prepared by an anisotropic bulk silicon wet etching process. After this process is etched, an angle greater than 90° will be formed between the side wall and the bottom of the cavity, which is not conducive to reducing the chip area and reducing the utilization rate of the silicon wafer. This is also an important reason why the development of the island membrane structure pressure sensor is restricted.

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