Metal ion deposition from ionized mangetron sputtering discharge

Abstract

A technique has been developed for highly efficient postionization of sputtered metal atoms from a magnetron cathode. The process is based on conventional magnetron sputtering with the addition of a high density, inductively coupled rf (RFI)plasma in the region between the sputteringcathode and the sample. Metal atoms sputtered from the cathode due to inert gas ion bombardment transit the rf plasma and can be ionized. 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 mTorr and can reach 85% at 30 mTorr. Optical emission measurements show scaling of the relative ionization to higher discharge powers. The addition of large fluxes of metal atoms tends to cool the Ar RFIplasma, although this effect depends on the chamber pressure and probably the pressure response of the electron temperature. The technique has been scaled to 300 mm cathodes and 200 mm wafers and demonstrated with Cu, AlCu, 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.