Amorphous Silicon Nitride Thin Film Withstanding Up to 1700 °C: Structure and Thermal Conductivity

Amorphous silicon nitride (SiN_x) thin films are widely used in modern microelectronics and also as thermal barrier materials in combustion engines. The structure and thermal conductivity of amorphous SiN_x films upon thermal treatment are important to electronic device thermal management and thermal insulating protection of engine components. In this work, we observe dramatically different crystallization behaviors of the amorphous SiN_x thin films prepared by various CVD techniques. This result is attributed to the difference in H atom concentration, coordination structure, and Si/N atomic ratio of the films, which critically influences the crystallization kinetics. The LPCVD SiN_x thin film exhibits superior thermal stability, remaining fully amorphous up to 1550 °C, while the measured cross-plane thermal conductivity noticeably increases from 1.62 to 2.42 W m^-1 K^-1. The thermal conductivity change is understood by disclosing the atomic bonding and vibrational mode characteristics in the amorphous SiN_x thin film before and after annealing. Impressively, the LPCVD SiN_x thin film can endure up to 1700 °C for 20 h and still preserves a large content of the amorphous matrix, accounting for an ∼80% volume fraction. The present work provides important findings for the high-temperature stability of amorphous SiN_x thin films and offers new physical insights into the thermal transport physics of amorphous dielectric solids.