Effect of sputtering power on piezoresistivity and interfacial strength of SiCN thin films prepared by magnetic sputtering

SiCN ceramics show large potential in high temperature pressure sensors with excellent stability up to 1000 °C, as it is changeling for the most of the existing pressure sensors to work stably at a temperature above 600 °C. However, bulk SiCN ceramics are not compatible to microelectronic processing and exhibit slow response due to viscoelasticity, it is necessary to propose alternative method to prepare SiCN functional structures. In this work, SiCN piezoresistive thin films are prepared by magnetron sputtering, and the influence of sputtering power on their piezoresistive properties and interfacial strengths are studied. The gauge factors of SiCN films range from 2786 to 4714 at various sputtering powers, which are significantly higher than the range from 46 to 1105 for existing piezoresistive thin films. Upon an optimal sputtering power of 75 W for silicon nitride target, the obtained SiCN sample show the largest gauge factors in a large range from 0.5 to 3.4 MPa. Furthermore, the SiCN thin films present high critical loads up to 36.5 N in scratch tests and indicate strong interfacial adhesion with substrate. This work provides an important reference for developing SiCN-based MEMS pressure sensors.