Guanidinate-Stabilized Monomeric Hafnium Amide Complexes as Promising Precursors for MOCVD of HfO₂

Abstract

Novel guanidinato complexes of hafnium [Hf{eta2-(iPrN)2CNR2}2(NR2)2] (R2 = Et2, 1; Et, Me, 2; Me2, 3), synthesized by insertion reactions of N,N'-diisopropylcarbodiimide into the M-N bonds of homologous hafnium amide complexes 1-3 and {[mu2-NC(NMe2)2][NC(NMe2)2]2HfCl}2 (4) using a salt metathesis reaction, are reported. Single-crystal X-ray diffraction analysis revealed that compounds 1-3 were monomers, while compound 4 was found to be a dimer. The observed fluxional behavior of compounds 1-3 was studied in detail using variable-temperature and two-dimensional NMR techniques. The thermal characteristics of compounds 1-3 seem promising for HfO2 thin films by vapor deposition techniques. Metal-organic chemical vapor deposition experiments with compound 2 as the precursor resulted in smooth, uniform, and stoichiometric HfO2 thin films at relatively low deposition temperatures. The basic properties of HfO2 thin films were characterized in some detail.

Atomic Layer Deposition of HfO2 Thin Films Employing a Heteroleptic Hafnium Precursor

“…In the past, we have modified the physico-chemical properties of hafnium amides in an attempt to improve the thermal stability of the parent hafnium amides. [15,16] This was achieved by introducing chelating ligands such as guanidinates and malonates into the hafnium metal ligand sphere with the specific intention of enhancing the thermal stability. This concept was attempted for all the three parent hafnium amides [Hf(NR 2 ) 4 ] (R ¼ Me, Et, EtMe), and we were successful in obtaining six coordinated Hf complexes which showed improved thermal properties.…”

“…This concept was attempted for all the three parent hafnium amides [Hf(NR 2 ) 4 ] (R ¼ Me, Et, EtMe), and we were successful in obtaining six coordinated Hf complexes which showed improved thermal properties. [15][16][17] The application of these so called ''designer'' precursors was very successful in state-of-the-art metal-organic (MO)CVD reactors. [18] In particular, the mixed Hf-amide-guanidinate class of precursors showed promise for the growth of high quality HfO 2 thin films by MOCVD exhibiting promising electrical properties.…”

“…The precursors employed, namely bis(dimethylamido)-bis(N,N(-diisopropyl-2-dimethylamido-guanidinato)hafnium(IV) (compound 1) and compound 2, were synthesized following literature procedures [15]. All reactions were performed with a conventional vacuum/argon line using standard Schlenk techniques.…”

Heterobimetallic complexes of lanthanide and lithium metals with dianionic guanidinate ligands: Syntheses, structures and catalytic activity for amidation of aldehydes with amines

“…Recently, we have addressed that phenoxides [20] and bridged bisamidinate complexes [21] of lanthanide and alkali metals are much more active catalysts for amidation of aldehydes with amines under mild conditions in comparison with their monolanthanide partner. Now we are particularly interested in synthesis and reactivity of bimetallic complexes with guanidinate ligands because monoanionic guanidinates have widely been used in organolanthanide chemistry as ancillary ligands [22][23][24][25][26][27][28][29][30][31][32]. Moreover, trisguanidinate lanthanides complexes can also serve as effective catalysts for polymerization of lactone [33][34][35] and for amidation of aldehydes with amines [36].…”

Mixed Amido/Imido/Guanidinato Complexes of Tantalum: Effects of Ligand Substitution on Thermal Properties

“…The use of guanidinates has already shown promising results for the deposition of Ti(C)N or HfO 2 thin films in CVD processes. [4,5] Moreover, we recently published a communication on the synthesis and characterization of mixed amido/imido/guanidinato complexes 3-5 and showed the successful deposition of conductive, almost carbon-free TaN (C content Ͻ 1 %) thin films using compound 4 as a single source precursor.…”