Introduction

1. O O- K+ K-SORBATE AS A PASSIVATOR IN COPPER CHEMICAL MECHANICAL PLANARIZATION (CMP) SLURRIES M. Nagar 1, J. Vaes 2, Y. Ein-Eli1 • Corrosion & Applied Electrochemistry Laboratory (CAE), Department of Materials Engineering, Technion , • Israel Institute of Technology, Haifa 32000, Israel • 2. IMEC, Kapeldreef 75, B-3001 Leuven, Belgium Introduction Chemical mechanical polishing (CMP) is a widely used technique for the planarization of metal and dielectric films to accomplish multilevel metallization. The fabrication of these layers without defects requires significant improvements in the CMP process. The success of CMP operations depends on the rate of material removal and the quality of the surface finish. The need to study copper inhibitors for CMP slurries is essential in order to achieve better performance of Cu CMP in future technology nodes. This study examines an application of a new inhibitor, potassium sorbate K[CH3CH=CHCH=CHCO2] in copper CMP slurries. CMP slurry composition was engineered in order to have a substantial copper removal, without compromising the capability to produce enhanced copper passivity. CMP results obtained on patterned wafers are presented illustrating the effect of sorbate concentration on CMP performance. Constant current density over wide potential range Sorbate characteristics The interesting ability of sorbate ion to protect copper surface is ascribed mainly to the primer encoring carboxylate group. After absorption, this would cause alignment of the dissolved short chain, normal to the copper surface, thus producing a thin, compact and protective layer. Figure 1 presents anodic polarizations of copper with and without sorbate. The constant current density over wide potential range implies an impressive stability of sorbate protective film. Comparable anodic polarization without sorbate is presented as well, exhibiting an active dissolution of copper and higher current densities at E(OCP) . Sorbate solution shift to noble region Results Complexing agent Without sorbate Figure 1 :Anodic polarizations of copper with and without sorbate. wafer performance Copper CMP performance with patterned wafers is presented, showing the importance in having a good passivator during CMP process: Figure 2 shows a decrease in dishing values with an increase in sorbate concentration. Figure 3 presents SEM images of 90nm Meander fork, showing dissolution of copper along lines with low sorbate concentration. Figure 4 shows optic microscope images of copper bonpads, illustrating higher polishing uniformity in high sorbate concentration. Dishing vs K-sorbate concentration Figure 3 polishing Uniformity 0.03M sorbate 1.7M sorbate HRP Scan of VDP80µm2 structure 1.7M sorbate 0.03M sorbate Figure 2 Figure 4 Cu loss Cu dished out Edge die Center die Summary and conclusions CMP results obtained on blanket and patterned wafers illustrate the effect of sorbate concentration on CMP performance: an increased sorbate concentration in model Cu slurries provides lower dishing values of copper in patterned wafers. The high solubility of sorbate in water (up to 9Molar) is a major advantage for CMP processing. A further reduction of the dishing values can be expected when using higher concentrations of dissolved sorbate in the slurry.