Lewis-base copper(I) formates: Synthesis, reaction chemistry, structural characterization and their use as spin-coating precursors for copper deposition

Consecutive synthesis methodologies for the preparation of a series of copper(I) formates [LmCuO2CH] (L = nBu3P: 4a, m = 1; 4b, m = 2; 5, L = [Ti](CCSiMe3)2, m = 1, [Ti] = (η5-C5H4SiMe3)2Ti) and [LmCuO2CH·HO2CR] (L = nBu3P: 7a, m = 1, R = H; 7b, m = 2, R = H; 7c, m = 2, R = Me; 7d, m = 2, R = CF3; 7e, m = 2, R = Ph. L = (cC6H11)3P, R = H: 8a, m = 2; 8b, m = 3. L = (CF3CH2O)3P, R = H: 9a, m = 2; 9b, m = 3. L = (CH3CH2O)3P, R = H: 10a, m = 2; 10b, m = 3. L = [Ti](CCSiMe3)2; m = 1: 11a, R = H; 11b, R = Ph) is reported using [CuO2CH] (1) and L (2a, L = nBu3P; 2b, L (cC6H11)3P; 2c, L = (CF3CH2O)3P; 2d, L = (CH3CH2O)3P; 3, L = [Ti](CCSiMe3)2) as key starting materials. Addition of formic acid (6a) or carboxylic acid HO2CR (6b, R = Me; 6c, R = CF3; 6d, R = Ph) to the afore itemized copper(I) formates 4 and 5 gave metal–organic or organometallic 7–11. The molecular structures of 8a and 11a in the solid state are reported showing a threefold coordinated copper(I) ion, setup by either two coordinatively-bonded phosphorus atoms and one formate oxygen atom (8a) or two π-bonded alkyne ligands and one oxygen atom (11a). A formic acid molecule is additionally hydrogen-bonded to the CuO2CH moiety. The use of 7b as suitable precursor for the deposition of copper onto TiN-coated oxidized silicon wafers by the spin-coating process below 300 °C is described. Complex 7b offers an appropriate transformation behavior into metal phase by an elimination–decarboxylation mechanism. The morphology of the copper films strongly depends on the annealing conditions. A closed grain network densified by a post-treatment is obtained (8 °C min−1, N2/H2 carrier gas). Hydrogen post-anneal to 420 °C after film deposition gave a copper film showing resistivities from 2.5 to 3.7 μΩ cm. This precursor was also used for gap-filling processes.