Stabilization of very high-k tetragonal phase in Ge-doped ZrO2 films grown by atomic oxygen beam deposition

Abstract

Ge-doped ZrO2 thin films are prepared on SiON/Si substrates by atomic oxygen beam deposition. It is shown that, at low growth temperatures (225–360 °C) and by using only a low amount of Ge (3–6.2 at. %), it is possible to develop a pure tetragonal zirconia phase, which remains stable after 1050 °C annealing in N2. The dielectric permittivity (k) shows pronounced correlation with the structural details of the oxide film and is increasing with Ge content to a maximum value of 37.7, which is obtained for a 6.2 at. % Ge-doped sample grown at 225 °C. The dielectric permittivity enhancement upon doping is attributed to the increase in the ZrO2 tetragonal distortion, as inferred from x-ray diffraction data. Obtaining tetragonal ZrO2 with very high k-values at low deposition temperatures and with excellent thermal stability could be beneficial for the integration of this dielectric in scaled devices requiring low equivalent oxide thickness.