Investigation of AlMe₃, BEt₃, and ZnEt₂as Co-Reagents for Low-Temperature Copper Metal ALD/Pulsed-CVD

The reactions of AlMe 3, BEt 3, and ZnEt 2 with toluene solutions of the copper(II) complexes [CuL 2 ] {L = acetylacetonate (acac; 1 ), hexafluoroacetylacetonate (hfac; 2 ), N -isopropyl-β-ketiminate (acnac; 3 ), N, N -dimethyl-β-diketiminate (nacnac; 4 ), 2-pyrrolylaldehyde (PyrAld; 5 ), N -isopropyl-2-pyrrolylaldiminate (PyrIm i Pr; 6a ), N -ethyl-2-pyrrolylaldiminate (PyrIm Et; 6b ), and N -isopropyl-2-salicylaldiminate (IPSA; 7 )} were investigated, and most combinations were found to deposit metal films or metal powder at 50 °C or less. SEM and XPS of metal films deposited on ruthenium showed a range of morphologies and compositions, including pure copper (excluding oxygen content after atmospheric exposure). These nonaqueous solution screening studies provided a rapid and convenient means to identify the most promising [Cu II L 2 ] precursor/ER n co-reagent combinations for copper metal ALD/pulsed-CVD studies, and subsequent ALD/pulsed-CVD studies were performed using 6b in combination with AlMe 3, BEt 3 and ZnEt 2 . As in solution, the reactivity of these reagents (pulsed-CVD) followed the order ZnEt 2 ≈ AlMe 3 ≫ BEt 3 . Furthermore, at 120−150 °C, ZnEt 2 was used successfully to deposit smooth, conductive films composed of copper with 8−15% Zn. On the basis of CVD studies with ZnEt 2, zinc content appears to derive from a parasitic CVD process, which becomes more favorable above 120 °C, detracting from the goal of self-limiting deposition.