METAL-ION DEPOSITION FROM IONIZED MAGNETRON SPUTTERING DISCHARGE

A technique has been developed for highly efficient postionization of sputtered metal atoms from a magnetron cathode. The process is based o n conventional magnetron sputtering with the addition of a high densit y, inductively coupled rf (RFI) plasma in the region between the sputt ering cathode and the sample. Metal atoms sputtered from the cathode d ue to inert gas ion bombardment transit the rf plasma and can be ioniz ed. The metal ions can then be accelerated to the sample by means of a low voltage dc bias, such that the metal ions arrive at the sample at normal incidence and at a specified energy. The ionization fraction, measured with a gridded mass-sensitive energy analyzer is low at 5 mTo rr and can reach 85% at 30 mTorr. Optical emission measurements show s caling of the relative ionization to higher discharge powers. The addi tion of large fluxes of metal atoms tends to cool the Ar RFI plasma, a lthough this effect depends on the chamber pressure and probably the p ressure response of the electron temperature. The technique has been s caled to 300 mm cathodes and 200 mm wafers and demonstrated with Cu, A lCu, and Ti/TiN. Deposition rates are equal to or in some cases larger than conventional magnetron sputtering. A primary application of this technique is lining and filling semiconductor trenches and vias on a manufacturing scale.