Research On The Key Technology Of Designing And Processing Of Membrane-structured Graphene High Thermal Resistant Pressure Sensor

As the core of pressure monitoring and control in various environments in industrial control,MEMS pressure sensors have been widely used in aerospace,weaponry,and civil fields due to their small size,low cost,and excellent performance.The two-dimensional nanomaterial graphene’s unique hexagonal honeycomb lattice structure brings it excellent mechanical,electrical,thermal,and other properties.It has become the preferred material for a new generation of micro-nano sensors.High temperature pressure sensors are strictly controlled by developed countries in the western world’s,the application of graphene in high temperature pressure sensors will have a profound impact on breaking through foreign technology blockade and realizing self-development of products.In this paper,a graphene high temperature pressure sensor based on Si₃N₄ protective film is proposed,which mainly completes the sensor structure design,process design and processing,Piezoresistive performance and thermal characteristic tests.The main research contents are as follows:Firstly,the structure design of the high thermal resistant graphene pressure sensor is completed based on the piezoresistive effect,and the optimal size of the elastic diaphragm is calculated by combining the small deformation theory of thin plate and finite element analysis method.The sensitivity of graphene is determined according to the maximum strain cell optimal layout and shape size.Then completed the sensor chip and bonding substrate process formulation and lithography layout design.Focusing on the preparation of silicon elastic diaphragm,the clean transfer of graphene sensitive junction,the deposition of high-reliability Si₃N₄ nanofilm,and the high-compatibility Au/Sn bonding gas,The tight packaging technology completes the chip sample preparation and completes the design of the external detection circuit of the graphene pressure sensor.Finally,the membrane structure graphene high thermal tesistant pressure sensor was characterized and tested.Mainly completed the graphene transfer quality and protection quality characterization,Au/Sn bonding air tightness packaging performance,pressure sensor performance testing.The surface of the graphene-sensitive junction has no apparent damage,wrinkles,photoresist residues,and other defects,and the Si₃N₄ nanofilm has stable electrical properties and high quality after protection.The element composition meets the requirements of the composition ratio of high-strength alloys.The sheer force and leak rate tests both meet the relevant standard needs.The static performance test results show that in the pressure range of 0～20 MPa（Traditional graphene pressure sensor measurement range:<0.5 MPa）,the sensitivity of the graphene pressure sensor is 55.072m V/V/MPa,repeatability and hysteresis error are 4.062%FS,2.118%FS.In addition,the thermal resistance test results show that the graphene-sensitive cell protected by Si₃N₄ has high stability under the high-temperature shock of 200°C,and the maximum resistance change is only 8.48%.And the temperature characteristics of the sensor 25℃～130℃show that graphene has a positive thermal effect,which has high repeatability and stability.