Abstract:
Failure of Integrated Circuits (IC) due to maintenance of diffusion barrier property is a major concern in the semiconductor industry. Hence, cobalt (Co) and ruthenium (Ru) are introduced as new promising barrier metals. After deposition of the metals, better surface uniformity is required for further level metallization for which Chemical Mechanical Planarization (CMP) is opted. The main rational behind using CMP process is the removal of interconnect and barrier metal without excessive thinning. This demands a slurry which gives a removal selectivity of 1:1. In the present work, slurries giving desire removal selectivity for Ru/Cu and Co/Cu CMP are proposed.
In the initial part of the study, an optimized formulation of slurry for CMP of Copper (Cu) as interconnect material and Ruthenium (Ru) as barrier line with removal selectivity is investigated. Thermogravimetric analysis (TGA), effect of abrasives concentrations, pH and solution temperature on etch rate are also examined. The results revealed that a Ru-Cu selectivity of ~1.003: 1 is obtained using 2 wt. % fumed silica, 0.2 M potassium iodate (KIO3) and 5 mM 1,2,3 Benzotriazole (BTA) based slurry.
CMP of interconnect metal copper and barrier metal cobalt using NaOCl based slurry is investigated as the second objective in this study. The slurry consists of 2 wt. % silica, 0.5 wt. % NaOCl and 5 mM BTA as inhibitor. It is seen that the formulated slurry gives a combination of low etch rates and comparatively fair removal rates along with selectivity of ~1:1.006 at pH 9, which are desired to be used in semiconductor industry
