Research On Piezoresistive Pressure Sensor Based On Porous Silicon SON Process

As one of the earliest MEMS sensor products,pressure sensors have been developed for about seventy years.With the rapid development of the MEMS industry,the current pressure sensors are moving towards intelligence,miniaturization and integration.The pressure sensor is the most widely used pressure sensor due to its simple structure and low manufacturing cost.It is easy to integrate and measure.At present,the typical piezoresistive pressure sensor in the industry adopts bulk silicon process manufacturing method.Firstly,the front surface of the silicon substrate is doped to form piezoresistance,then the back surface of the substrate is etched with anisotropic silicon cup by alkaline solution,and finally the pressure cavity is formed by bonding technology.The piezoresistive pressure sensor prepared by the method is convenient for mass production,stable in structure and reliable in function,but the process flow is complex and is not conducive to miniaturization and integration of devices.This paper abandons the traditional silicon cup bonding scheme,adopts the surface silicon process manufacturing method,uses the porous silicon material as the sacrificial layer,and then uses the epitaxial process to form the silicon film layer structure above the cavity to manufacture the piezoresistive pressure sensor with simple process flow,IC compatibility,easy integration and miniaturization.In this paper,the function and reliability of the piezoresistive pressure sensor are tested.The sensitivity gain is 0.015mv/mbar,the temperature coefficient is equivalent to that of market products,and the reliability welding,temperature cycling and drop tests are qualified.The expected goals of reducing chip size and simplifying process flow were achieved.The work of this paper is mainly divided into four parts:1.The sensitive mechanism of piezoresistive pressure sensor is analyzed,and the key process parameters that affect the sensitivity of piezoresistive pressure sensor are obtained,and the modeling and simulation analysis are carried out by using the software conventor.2.The characteristics of porous silicon material and SON process based on porous silicon sacrificial layer are analyzed,and the key process parameters are obtained.The process parameters for forming the elastic film layer structure above the cavity are finally confirmed through single process experiment.3.Design the whole process scheme of piezoresistive pressure sensor based on porous silicon SON process,and complete the manufacture of piezoresistive pressure sensor.4.Test the function and reliability of the packaged piezoresistive pressure sensor.The results show that the sensitivity gain of the piezoresistive pressure sensor sample is 0.02mv/torr,thus achieving the expected goals of reducing the chip size and simplifying the process flow.