Study of Y2O3 Thin Film Prepared by Plasma Enhanced Atomic Layer Deposition

Atomic layer deposition (ALD) is a promised thin film deposition technique to fabricate nanometer scale thin films. Unlike chemical vapor depositions (CVDs), one cycle of ALD process is composed of separated precursor pulsing step, purging step and reactant pulsing step. Due to separated steps in an ALD process, precise thickness control of thin films is available. Step coverage, uniformity and conformality of thin films are also superior compared with other thin film techniques, such as sputter, pulsed laser deposition (PLD).

Plasma enhanced atomic layer deposition (PEALD) is energy reinforced ALD technique by inserting plasma. In case of a direct PEALD, plasma is induced during the reactant step to improve reactivity of reactant. The ALD window of PEALD is expanded especially at lower temperature due to high reactivity of plasma species. Better quality of thin films is available due to decreased contaminations within thin films and improved stoichiometry of thin films.

Y₂O₃ has wide band gap, good thermal stability, and high dielectric constant. Due to these characteristics, Y₂O₃ is used for various applications, such as, replacement of SiO₂ in complementary metal oxide semiconductor (CMOS) devices, protective coatings, and buffer layers for ferroelectrics and superconductors. Y₂O₃ is also used to fabricate Yttria-stabilized zirconia (YSZ) which is the most typical electrolyte material for solid oxide fuel cells (SOFCs).

In this study, we prepared Y2O3 thin films by direct PEALD. Tris (methylcyclopentadienyl) yttrium ((MeCp₃)₃Y) precursor is used as a precursor of Y₂O₃ and high purity oxygen gas with O₂ plasma is used as the reactant. The growth rate of Y₂O₃ thin films are measured by ellipsometer as a function of deposition temperature. Physical and chemical characteristics of Y2O3 thin films are also investigated which is deposited at different temperature.