MEMS pressure sensor and preparation method thereof

Abstract

The invention relates to an MEMS pressure sensor and a preparation method thereof. The MEMS pressure sensor comprises a pressure sensitive film, at least four front-side voltage dependent resistors and at least four back-side voltage dependent resistors, the pressure sensitive film includes a front side and a back side, each front-side voltage dependent resistor is arranged at the front side of the pressure sensitive film, each back-side voltage dependent resistor is arranged at the back side of the pressure sensitive film, and the front-side voltage dependent resistors and the back-side voltage dependent resistors are electrically connected to form a Wheatstone bridge. The change direction of the resistance, along with the pressure, of the front-side voltage dependent resistor is opposite to that of the resistance, along with the pressure, of the back-side voltage dependent resistor at the corresponding position, so that errors caused by technical conditions and / or external factors of the voltage dependent resistors are offset, and the output stability and precision of the MEMS pressure sensor are improved.

Description

technical field [0001] The invention relates to the field of micro-electro-mechanical systems (Micro-Electro-Mechanical Systems, MEMS), in particular to a MEMS pressure sensor and a manufacturing method thereof. Background technique [0002] MEMS pressure sensor is a kind of thin film element, which is suitable for sensing pressure. It has the advantages of small size, light weight, high precision, high sensitivity and low cost. It has replaced traditional sensors in many fields. With the rapid development of microelectronics technology, the application range of MEMS pressure sensors is becoming more and more extensive. At present, they are widely used in automotive systems to measure air bag pressure, fuel pressure, engine oil pressure, intake pipe pressure and tire pressure. It can be applied to pressure measurement in the medical market and other industrial fields. [0003] At present, the mainstream MEMS pressure sensor is based on the principle of piezoresistor. When t...

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Problems solved by technology

[0004] A problem that needs to be considered more in MEMS devices is its sensitivity to temperature and pressure. For piezoresistive MEMS pressure sensors, such problems must be considered. Therefore, MEMS pressure sensors still have some problems and defects. It is because in the traditional structure, the resistance values ​​of the four resistors are equal, the piezoresistive coefficients of the adjacent resistors are opposite, and the piezoresistive coefficients of the two opposite resistors are the same, but usually due to the limitation of process errors or external interference factors, the four The static values ​​of the two resistors will not match exactly, causing the four resistors to not be exactly equal and the Wheatstone bridge to be unbalanced

Therefore, during the working process of the MEMS pressure sensor, as the temperature changes, the resistances with unequal resistances will change differently with the temperature, which will cause the absolute reference of the pressure sensor to change.

In addition, the four piezoresistors of the Wheatstone bridge are absolutely symmetrical on the MEMS chip, but for the entire packaged chip, the four piezoresistors are not symmetrical, and when the temperature or stress changes, the pressure sensitive film will be damaged. Deformation, which in turn causes changes in the varistor, but the change value of the varistor will not be exactly the same

As a result of the above situation, the output of the pressure sensor will still change when there is no pressure change, resulting in instability of the output, which is manifested by a relatively large temperature drift.

[0005] The problems and defects of traditional MEMS pressure sensors limit its application range. With the continuous development of science and technology, the demand for MEMS is also increasing. Therefore, it is more accurate to solve the problems in the existing technology and further research The MEMS pressure sensor imperative

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