The growth nature of copper phthalocyanine thin-film from a monolayer to 20 nm thickness on hydrogen-terminated flat Si(l I l) was studied with MBE-STM and other complementary techniques. The molecules were found to adsorb randomly at 60"C for surface coverages up to around one monolayer, but, form an ordered structure above a few monolayers. At higher temperature (> 140'C), crystalline nuclei were observed from the very beginning of the growth and the remaining area was not fully covered by the molecules. These results suggest that the stacking of the molecules of more than a few monolayers is necessary to form an ordered two-dimensional lattice on this surface.