Cu films deposited by a partially ionized beam (PIE)

Abstract

A partially ionized beam (PIE) source for formation of Cu thin films is characterized by measuring ion beam current density at various acceleration voltages (V-a) and ionization potentials (V-I). Increase of ion beam current density is intimately related with the variation of electron emission current in ionization of vaporized Cu particles. In X-ray diffraction (XRD) spectra of deposited Cu films on Si (100) substrate, preferred orientations along the [111] and [200] axis only can be found and relative intensity ratio of R=I[111]/I[200] is increased as V-a is raised. At V-a=4 kV, R reaches the value of 29.4 which indicates that the deposited films is in a sense epitaxially grown. After annealing at 500 degrees C for 30 min, XRD spectra of the films do not show any difference in peak intensity and preferred orientations as before. In consequence, the Cu films deposited by PIE have thermally stable;structure, Resistivity of the deposited Cu films is reduced as acceleration voltage is increased and is 2.14 mu Omega cm at V-a=3 kV, and the value is a little reduced to a value of 2.07 mu Omega cm after annealing. Adhesion of the Cu/Si system is examined by a scratch test and critical load to cause adhesion failure is increased to about 17 newton at V-a=3 kV, which is four times higher than that of V-a=0 kV.