Structure evolution of atomic layer deposition grown ZrO2 films by deep-ultra-violet Raman and far-infrared spectroscopies

Zirconium dioxide is one of the candidates for substitution of SiO2 as dielectric gate in complementary metal-oxide-semiconductor devices. In this work, 64 and 107 nm thick ZrO2 films were grown on Si(100) using atomic layer deposition, which produces uniform and conformal layers, as required in microelectronics. Structural investigation was made using ultra-violet Raman spectroscopy and far-infrared transmission spectroscopy. With the use of a 5.0 eV excitation in Raman spectroscopy thin films can be measured because of the enhancement of the Raman efficiency, the reduction of the photoluminescent background, and the elimination of the signal of the silicon substrate. Far-infrared spectroscopy reveals also information on the material structure because in the 100-700 cm-1 frequency range the infrared radiation resonates with optical phonons. The strength and absorption frequency of the latter depend indeed on the details of the material structure. From our work we conclude that the relative amount of tetragonal and monoclinic phases in the ZrO2 films changes with film thickness and annealing procedure. The observed trend suggests that the increase of the thickness of the film, as well as the thermal annealing at 950 °C for 30 s, produce an increase of the relative amount of the monoclinic phase. © 2003 Elsevier B.V. All rights reserved.