Self-Supporting Ultrathin DLC/Si3N4/SiO2 for Micro-Pressure Sensor

In this study, we firstly reported a micropressure sensor based on self-supporting diamond-like carbon (DLC)/Si3N4/SiO2 films with total thickness of 785 nm, where the DLC film was fabricated by a facile DC magnetron sputtering process. Particularly, the DLC film was selected as a hybrid sensitive and structural material due to its superior mechanical, piezoresistive properties and stability under harsh environment. Results showed that the sensitivity of the integrated sensor could reach 5.3 x 10(-5)/kPa within the pressure range of 0-60 kPa, together with the nonlinearity and the hysteresis was 5.7% FS (full scale) and 0.8% FS, respectively (at 20 degrees C). Most importantly, without any thermal insulation package, the sensitivity only changed slightly within +/- 7.0% even the temperature varied dramatically from -20 degrees C to 100 degrees C. Such excellent performance of the sensor was mainly originated from the good stability of atomic bond structure in DLC films, which was confirmed by the variable-temperature XPS test. In addition, the signal could be further compensated by the DLC thermal compensation resistor in which the temperature coefficient of resistance (TCR) was about -1247.3 ppm/degrees C. These results bring forward a promising strategy to fabricate themicro-pressure sensor with high structural sensitivity, stability as well as lightweight design for micro-electromechanical system (MEMS) used in harsh applications.