Optimization of sputtered Cr/Au thin film for diaphragm-based MEMS applications

An optimization study on the sputtering of Cr/Au thin film for diaphragm-based MEMS applications is presented. The effects of the film thickness, process pressure and process power on the residual stress of the film are investigated. A low-stress silicon nitride diaphragm-based device characterization platform is fabricated to study the influence of the Cr/Au film stress on the diaphragm compliance. The fabricated devices are characterized by measuring the capacitance change under a bias voltage from 0 to 40 V. For the 8-µm and 10-µm air gap device characterization platforms, the largest capacitance changes of 5.1% and 4.3%, respectively, occur at a compressive film stress of − 200 MPa. A large capacitance change indicates a more sensitive diaphragm, which is desired in pressure sensor design.