Effect of interfacial fluorination on the electrical properties of the inter-poly high-k dielectrics

In this paper, the reliabilities and insulating characteristics of the fluorinated aluminum oxide (Al2O3) and hafnium oxide (HfO2) inter-poly dielectric (IPD) are studied. Interface fluorine passivation has been demonstrated in terminating dangling bonds and oxygen vacancies, reducing interfacial re-oxidation and smoothing interface roughness, and diminishing trap densities. Compared with the IPDs without fluorine incorporation, the results clearly indicate that fluorine incorporation process is effective to improve the insulating characteristics of both the Al2O3 and HfO2 IPDs. Moreover, fluorine incorporation will also improve the dielectric quality of the interfacial layer. Although HfO2 possesses higher dielectric constant to increase the gate coupling ratio, the results also demonstrate that fluorination of the Al2O3 dielectric is more effective to promote the IPD characteristics than fluorination of the HfO2 dielectric. For future stack-gate flash memory application, the fluorinated Al2O3 IPD undoubtedly possesses higher potential to replace current ONO IPD than the fluorinated HfO2 IPD due to superior insulating properties.