Atomic Layer Deposition of TiO₂ and ZrO₂ Thin Films Using Heteroleptic Guanidinate Precursors

Abstract

Review: This review provides a brief description of ALD and presents studies on the deposition of thin films of groups 4 and 5 metal oxides using ALD. A description of the general ALD properties of homoleptic precursors, in addition to a review of the thermal ALD of groups 4 and 5 metal oxides from heteroleptic precursors, is presented. Trends in the properties of heteroleptic ALD precursors based on the literature review and recent experimental data are discussed. Full Paper: Atomic layer deposition of TiO 2 and ZrO 2 is performed using heteroleptic amido/guanidinate metal precursors, and ozone and water as oxygen sources. The results are compared to previous studies and the effect of the ligands on the precursor properties are discussed.

Titanium dioxide thin films by atomic layer deposition: a review

“…Ti(NEtMe) 3 (guan-NEtMe) with H 2 O and O 3 . This ALD route exhibits rather constant GPC around 0.3-0.4 Å/cycle between 200 °C and 325 °C, independent on the oxygen source used [790]. For the water (for ozone not reported) process the GPC at 350 °C drops slightly, which hints absence of decomposition at such a high temperature.…”

“…For the water (for ozone not reported) process the GPC at 350 o C drops slightly, which hints absence of decomposition at such a high temperature. The stability is notably enhanced in comparison to the Ti(NEtMe)4 precursor [767], perhaps due to chelate effect of the guanidinate ligand [790]. The ozone-based process yields very pure films with 1.3 at.% for carbon, 0.3 at.% for nitrogen and 0.5 at.% for hydrogen, whereas the water-based process incorporates more impurities into the films, such that the levels are 4.7 at.% for carbon, 1.6 at.% for nitrogen and 0.5 at.% for hydrogen.…”

“…The ozone-based process yields very pure films with 1.3 at.% for carbon, 0.3 at.% for nitrogen and 0.5 at.% for hydrogen, whereas the water-based process incorporates more impurities into the films, such that the levels are 4.7 at.% for carbon, 1.6 at.% for nitrogen and 0.5 at.% for hydrogen. The impurity levels are reflected to the crystallization temperature of the films such that for the ozone-based process anatase-structured films are obtained at 275 o C (amorphous below), while for the water-based process the films grow with the anatase structure at 300 o C (amorphous below) [790].…”

Atomic layer deposition of zirconium dioxide from zirconium tetrachloride and ozone

“…Often, both precursors contain hydrogen and thus the residual hydrogen content could be diminished after substituting either one or both precursors by hydrogen-free ones. ZrO 2 films have been grown by several water-free ALD processes [21], such as in those based on (C 5 H 5 )Zr(N(CH 3 ) 2 ) 3 and oxygen plasma [7,22], Zr[N(CH 3 ) 2 ] 4 and O 3 [14], Zr[N(CH 3 )(C 2 H 5 )] 4 and O 3 [6,9,11,23], Cp 2 ZrCl 2 and O 3 [13,24], or Zr(NEtMe) 3 (guanNEtMe) and O 3 [25]. Regarding metal halide based and hydrogen-free ALD processes, depositions of Al 2 O 3 from AlCl 3 and O 3 [26], TiO 2 from TiCl 4 and O 3 [27], Ta 2 O 5 from TaCl 5 and O 3 [28], HfO 2 from HfCl 4 and O 3 [29], and HfO 2 from HfI 4 and O 2 [30] have been reported.…”

Reaction mechanism of atomic layer deposition of zirconium oxide using zirconium precursors bearing amino ligands and water

“…Currently, using high-κ gate dielectrics to replace SiO 2 is an effective method for solving the problem. Because of the high dielectric constant and thermodynamic stability, zirconium oxide (ZrO 2 ) has been used as gate dielectrics via the ALD method for MOSFET devices (Gaskell et al, 2007;Dezelah IV et al, 2008;Kaipio et al, 2014;Jung et al, 2015;Kanomata et al, 2016;Mahuli et al, 2021;Xu et al, 2021).…”