AVS 49th International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuA

Paper TF-TuA3
Effect of Growth Temperature on the Properties of ALD Grown ZrO@sub 2@ Films

Tuesday, November 5, 2002, 2:40 pm, Room C-101

Session: Atomic Layer Deposition - Oxides
Presenter: G. Scarel, Laboratorio MDM-INFM, Italy
Authors: G. Scarel, Laboratorio MDM-INFM, Italy
E.K. Evangelou, Laboratorio MDM-INFM, Italy
S. Ferrari, Laboratorio MDM-INFM, Italy
S. Spiga, Laboratorio MDM-INFM, Italy
C. Wiemer, Laboratorio MDM-INFM, Italy
M. Fanciulli, Laboratorio MDM-INFM, Italy
Correspondent: Click to Email
Zirconium dioxide films, 15 nm thick, are grown by atomic layer deposition (ALD) using zirconium tetrachloride and water as precursors. A relatively high dielectric constant (22), wide band gap and conduction band offset (5.8 eV and 1.4 eV respectively) indicate zirconium dioxide as one of the most promising candidates to substitute silicon dioxide as gate dielectric in complementary metal-oxide-semiconductor devices. However, crystallization occurring both during deposition and after annealing treatment affects charge mobility and induces flat band voltage shifts. Chlorine ions might contribute to the same effects and also to an increase of leakage current related to the introduction of extra levels in the band gap. These ions are produced during the stage of the ALD cycle in which the ZrCl4 precursor reacts with the growing surface. To address the structural and morphological properties and their effects on the electrical ones, ZrO2 films are grown at different substrate temperatures: 150 C, 200 C, 250 C, 300 C and 350 C. Relevant modifications of film structure with changing the substrate temperature during growth are expected because the density of the reactive sites (mainly Si+1 - (OH)-1 bonds) decreases with increasing temperature (Y.B. Kim et al., Electrochem. and Solid State Lett. vol. 3 (2000) p. 346). Preliminary results suggest, for example, that the amorphous component of the films increases with higher density of Si+1 - (OH)-1 bonds in the starting growth surface obtained at lower substrate temperatures. The size and consequences of these modifications are investigated in this work using x-ray diffraction and reflectivity, far infrared transmission spectroscopy and atomic force microscopy. Time of flight - secondary ion mass spectrometry is used to study chlorine and oxygen diffusion and to what extent the behavior of these two species is related. Electrical properties are determined from C-V and J-V characteristics.