Moisture-absorption-induced permittivity deterioration and surface roughness enhancement of lanthanum oxide films on silicon

Effects of moisture absorption on permittivity and surface roughness of lanthanum oxide (La2 O3) films were investigated. It was found that the moisture absorption deteriorates the permittivity (k) of La2 O3 films on silicon because of the formation of hexagonal La (OH)3 with a low permittivity after films were exposed to the air. Therefore, the moisture absorption should be a very possible reason for the permittivity variation of La2 O3 film in literatures reported, so far. Furthermore, a roughness enhancement was also observed after La2 O3 films were exposed to the air for several hours. This observation should be another concern of hygroscopic La2 O3 film application.