a liquid organocuprous compound of formula of the present invention can be conveniently used in a low - temperature cvd process for the production of a contaminant - free copper film having good step - coverage and hole - filling properties : ## str1 ## wherein : r 1 represents a c 3 - 8 cycloalkyl group , and r 2 and r 3 are each independently a perfluorinated c 1 - 4 alkyl group .