Room-temperature growth of Cu thin films by nozzle-type partially ionized beam deposition with various acceleration voltages

Abstract

Nozzle-type partially ionized beam deposition of Cu thin films at a system pressure of 5 x 10(-6) to 7 x 10(-6) Torr was conducted in order to fabricate Cu metallization with high-quality Cu/Si interfaces. In order to prevent diffusion of the Cu toward the Si and silicide formation, the depositions with various acceleration voltages were performed at room temperature. X-ray diffraction patterns showed all the as-grown films having the [111] Cu direction normal to the (100) Si plane regardless of the acceleration voltage. Anger electron spectroscopy demonstrated that there was no residual carbon detection in the bulk of the as-grown films. The thickness of the all as-grown Cu films was 2 000 Angstrom as confirmed by low-magnitude cross-sectional transmission electron microscopy, i.e. growth rates of the Cu film by partially ionized beam deposition at room temperature were almost independent of the acceleration voltage. Furthermore, cross-sectional transmission electron microscopy showed a sharp Cu/Si interface and large-grain polycrystalline Cu films with twin defects. Atomic force microscopy under ambient conditions showed all the films had very smooth surfaces which were greatly reduced with the acceleration voltage. A scratch test showed good adhesion in all the films. These results indicate that the nozzle-type partially ionized beam deposition at room temperature can be used for Cu thin film metallization for semiconducting applications.