Low temperature SiOx thin film deposited by plasma enhanced atomic layer deposition for thin film encapsulation applications

Silicon oxide (SiOx) films were synthesized by plasma enhanced atomic layer deposition (PEALD) using di-isopropylaminosilane [SiH3N(C3H7)2] as the precursor and an oxygen plasma as the reactant. The layers were characterized with respect to different growth temperatures between 60 and 150 °C. The film density and surface roughness values measured by x-ray reflectometry and atomic force microscopy all approached those of thermally grown SiOx. Also, reasonably high breakdown voltages were observed at all deposition temperatures. An interesting phenomenon involves the fact that the SiOx layer deposited at 60 °C is most effective as a moisture barrier, as it exhibits the lowest water vapor transmission rate. X-ray photoelectron spectroscopy analyses indicate that the silicon monoxide bonding characteristic becomes more pronounced as the growth temperature decreases. It is conjectured that such a difference in the bonding state renders the surface of the low temperature SiOx films rather hydrophobic, which suppresses the penetration of moisture. The results indicate that low temperature PEALD SiOx films may be suitable for thin film encapsulation applications in mechanical flexible platforms.