CHARACTERISTICS OF POLYIMIDE FILMS DEPOSITED BY IONIZED CLUSTER BEAM

Ionized cluster beam deposition (ICBD) technique has been employed to fabricate high-purity crystalline polyimide (PI) film. The pyromellitic dianhydride (PMDA) and oxydianiline (ODA) were co-deposited using dual ICB sources to form a polyamic acid film, which was subsequently thermally cured to form a PI film. Fourier transform infrared spectroscopy (FTIR), x-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM) studies show that the bulk and surface chemical properties and the crystalline structure are very sensitive to the ICBD conditions such as cluster ion acceleration voltage and ionization voltage. At optimum ICBD conditions, the PI films have a maximum imidization, negligible impurities (~1% isoimide), and a good crystalline structure probably due to the high surface migration energy, and surface cleaning effect. The weight average molecular weight as determined by quasielastic light scattering was found to be —45 000. These characteristics are superior to those of films deposited by other techniques such as solvent cast, vapor deposition, or sputtering techniques. © 1994, American Vacuum Society. All rights reserved.