Directional sputter deposition for semiconductor applications

Abstract

The deposition of metal and compound films from ions rather than neutrals allows a high degree of control over the incident particle's direction and energy. Metal-rich plasmas have been produced using large magnetrons (30 cm dia., 20 kW) and in-flight ionization of the sputtered atoms by means of a dense, inductively coupled rf plasma. This plasma is generated by a multi-turn antenna inside the chamber located between the cathode and the sample. The nature of the deposition, including the ion-to-neutral ratio and the ion energy are controllable. Relative ionization of the metal has been measured at over 80%. Ion energy is controlled by a negative dc sample bias. Metal films of Cu and AlCu have been deposited on 200 mm Si wafers at room temperature into moderate aspect ratio wafer features with no voids. The features used are trenches and vias of width >3500A, and the technique has also been used to fill 2-level, 'dual damascene' features. The films are highly (111) oriented and have low stress and low Ar content. The effects of ion direction as well as resputtering of the film topography are readily observed, and are consistent with computer model predictions. High quality TiN films (40 micro-Ohm-cm, gold colored) have also been deposited at room temperature into trenches and vias for applications as diffusion barriers.