Electronic structure of cerium oxide gate dielectric grown by plasma-enhanced atomic layer deposition

We have systematically investigated the electronic structure of CeO ₂ dielectric by plasma enhanced atomic layer deposition (PE-ALD). The CeO₂ films were deposited by using novel tris(isopropyl- cyclopentadienyl)cerium [Ce(iPrCp)₃] precursor and O₂ plasma. The energy band gap (3.48 eV), Fermi level (4.71 eV), and band offsets of PE-ALD CeO₂ were elaborately determined by combining spectroscopic ellipsometry and ultraviolet photoemission spectroscopy (UPS) techniques. In addition, based on the experimental results of Fowler-Nordheim(F-N) tunneling and Poole-Frenkel(P-F) conduction for Al/PE-ALD CeO₂/p-Si, the increased interfacial layer and reduced trapped oxide densities were found to be correlated to the increase in effective barrier height (0.89, 1.18 and 1.26 eV) and decrease in decreased trap energy levels (0.47, 0.26 and 0.18 eV) with increasing O₂ annealing temperature (400, 600 and 800C), respectively. These discrepancies might be attributed to the thin film characteristics and oxygen vacancies in the CeO₂ dielectrics, depending on the deposition techniques and post deposition annealing processes.