Quantitative measurement of nodule formation in W-Ti sputtering

Titanium-tungsten alloys have been used as a diffusion barrier between Si substrates and Al-based interconnect metallization for more than two decades. Due to the increasing complexity of integrated circuits, the primary concern has been focused on the reduction of particles during sputtering. Flaking of the redeposited nodules on the target surface was suspected to be one of the particulate sources. To control the nodule formation, a fundamental knowledge of the nodule formation mechanism is required. In this study, the influence of target properties and sputtering parameters on nodule formation in sputtering targets of tungsten with 10 and 15 wt % titanium was investigated. The amount and life of the nodules as a function of target life was determined. A parabolic relation showed a saturated nodule size with increased sputtering life. The existence of fractured nodules confirms the nodules to be the particulate source. (C) 1998 American Vacuum Society. [S0734-2101(98)09604-3].