Research On Preparation,Testing And Simulation Methods Of Sicn Piezoresistive Films

Aerospace,petrochemical,and automotive fields have put forward higher requirements for high-temperature sensor testing in harsh environments.However,the existing high-temperature pressure sensors are difficult to work stably at high temperatures exceeding 600℃.Recent studies have shown that Si CN ceramics in polymer-derived ceramics still have excellent stability at high temperatures and a piezores istance factor of 1000-4200.However,the piezores istive mechanism has not been clarified,and the preparation and analysis of the related film structure is of great significance to the development of micro-nano sensor devices.In this paper,the influence of different process conditions on the piezoresistive properties of Si CN films was studied by magnetron sputtering.The results show that when the carbon target power,silicon nitride target power and target base distance are 80 W,100 W,and 8 cm,respectively,the gauge factor of the Si CN film can be as high as 7290,which is much higher than the current one.Under pressures of 0.5,1.05,2.25,and 3.4 MPa,the gauge factors of the piezores istive film system are7290,5671,3502,and 2573,respectively,indicating that the material still has high sensitivity at a large range.In addition,the critical load range of Si CN thin film and silicon substrate prepared under various process conditions is 21.4～36.55 N,which proves that the films prepared by this method have good film-base bonding force.To further explore the mechanism of the piezoresistive performance of amorphous Si CN,first-principles methods are used to study the changes of the atomic structure and electronic properties of the models before and after compression.The results show that the distance between the free carbon conductive phase（～1.8（?））and the formation of Si-C bonds with the Si₃N₄ region are most conducive to the formation of tunneling effect and excellent piezoresistive performance.In addition,the calculated band gap change rate of the material before and after compression has the same trend as the resistance change rate in the experiment.The established calculation method can be used to evaluate the nanostructure-piezoresistive performance relationship of Si CN materials.The preparation and analysis methods of Si CN films proposed in this work provide an important reference for the development of new MEMS piezoresistive sensors.