(204d) Atomic Layer Deposited Y2O3 Thin Films Using Novel Cyclopentadienyl-Type Yttrium Precursor

The increased miniaturization of complementary metal oxide semiconductor transistors and memory storage capacitors is driving the need for ultrathin nanometer layered film structures of high dielectric constant (κ) metal oxides in order to replace SiO2 in gate oxide layer of transistors and charge storage media of capacitors. High-κ metal oxides including HfO2, ZrO2 and Y2O3, serve as potential candidates to replace SiO2 and enhance scaling limits of device manufacturing. Y2O3 has high dielectric constant (~15), good thermal stability, relatively large conduction band offset (2.3 eV), and valence band offset (2.2 eV). For these reasons, Y-containing films may likely help serve the needs for high dielectric insulating films in nanometer dimensioned transistors and memories.

In this study, thin films of Y2O3 are deposited on silicon using tris (ethylcyclopentadienyl) yttrium as the metal precursor and water as the oxidizer. The film growth kinetics of these films is examined as function of several deposition parameters. The deposition rate of Y2O3 films is 1.7 Å/cycle at 250 °C with self limiting growth characteristics. These films are subsequently analyzed using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and atomic force microscopy. The as-deposited Y2O3 films are also found to be stoichiometric with carbon content below detection limit as probed by XPS and amorphous in nature as indicated by XRD measurements. In addition, the properties of Y2O3-doped HfO2 films are investigated in the context of crystallization and interfacial behavior due to high temperature annealing. The HfYOx films of different compositions are grown by altering the deposition cycle ratio of the two metal precursors. The resulting films are then characterized after annealing at different temperatures using XRD and XPS. These results will be discussed in the context of high-κ materials for gate dielectric and capacitive memory applications.