Lanthanide N,N-Dimethylaminodiboranates: Highly Volatile Precursors for the Deposition of Lanthanide-Containing Thin Films

Abstract

New lanthanide CVD precursors of stoichiometry Ln(H₃BNMe₂BH₃)₃ have been prepared, where Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. The ligand is N,N-dimethylaminodiboranate, a new kind of multidentate borohydride. The structures of the Ln(H₃BNMe₂BH₃)₃ complexes are highly dependent on the size of the lanthanide ions: the coordination number decreases from Pr (CN = 14) to Sm (CN = 13) to Er (CN = 12) corresponding with the decrease in ionic radii. The Ln(H₃BNMe₂BH₃)₃ complexes are highly volatile and sublime at temperatures as low as 65 °C in vacuum. These complexes are useful CVD precursors; for example, Y(H₃BNMe₂BH₃)₃ has been used to deposit Y₂O₃ on silicon at 300 °C by CVD using water as a coreactant.