MICROSTRUCTURE OF COPPER-FILMS CONDENSED FROM A COPPER PLASMA WITH ION ENERGIES BETWEEN 2 AND 150 EV

A steady vacuum are with a consumable anode, the anodic vacuum are, was used to produce thin copper films with a thickness of 1 mu m. The degree of flux ionization and ion energy were manipulated by changing the geometric parameters of the are discharge and by biasing the substrate relative to the vacuum vessel. The films produced are homogeneous and dense, with a purity of about 99.995%. The films exhibit a metastable state, which recrystallizes at room temperature within a few days. As a characteristic parameter describing the creation of the metastability the product of ion energy and degree of flux ionization - the mean ion energy per atom - can be introduced. The grain size of the films is investigated with regard to process parameters such as the substrate temperature (50-500 degrees C), degree of flux ionization (the ratio of the ion flux to the total atom flux per unit area) (1%-30%) and ion energy (2-150 eV). The microstructure is different in comparison with the usual structure zone models and a new structure zone model is presented. Below a homologous temperature ($) over cap T(i.e. the ratio of substrate to melting temperature of the evaporated material) of 0.3 a metastable film structure exists if the mean ion energy exceeds 1 eV atom(-1) (zone M). The grain size is determined by an athermal growth process and no activation energy for the grain growth can be found. Above that temperature, a crystalline structure exists in zone K and here the grain size increases with increasing temperature and an associated activation energy for the grain growth can be observed. This activation energy is a function of the flux ionization X and increases from about 0.1 eV (X = 2%) to 0.39 eV (X = 27%).