Injection induced charging of HfO2 insulators on Si

Charge trapping in HfO2 films on Si(1 0 0) was studied using generation of electron–hole pairs in the oxide by 10 eV photons. The oxide deposition chemistry strongly influences the density and sign of the trapped charge: positive charge is observed in films obtained from HfCl4 and metallo-organics, while negative charge is dominant in the films grown from Hf(NO3)4. The weak dependence of the trapped charge on the HfO2 thickness suggests that charging is associated with a silicon oxide interlayer grown between the Si and HfO2 during deposition. The latter is affirmed by enhancement of the charging after oxidation of the samples at 650 °C, indicating the interfacial silicon oxide as being the key factor determining the electrical stability of the HfO2 insulating stacks.