Modified Abrasives based on fumed SiO 2 and Al 2 O 3 for the Cu CMP Process
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Modified Abrasives based on fumed SiO2 and Al2O3 for the Cu CMP Process D.Zeidler1, J.W.Bartha1, W.Lortz2, R.Brandes3 1
University Dresden, Germany Degussa AG, Hanau, Germany 3 Degussa Corporation, Piscataway, N.J., USA 2
Corresponding author:
J.W.Bartha, Dresden University, TUD/IHM - Mierdel-Bau, D-01062 Dresden Phone: +49 351 463 35292 Fax: +49 351 463 37172 [email protected]
ABSTRACT New abrasive particles based on SiO2 and Al2O3 were produced with different coating and doping. Seven specifically designed particles were dispersed to prepare slurries for Cu CMP. Glycin was used as complexing agent and hydrogenperoxid as oxidizer. The experimentally obtained removal rate, selectivity, surface quality and planarisation ability, demonstrate a significant impact of the different abrasives tested. SiO2 particles covered with Al2O3 increased the removal rate for Cu . In comparison to this behavior, a low rate for TaN proved a high selectivity copper removal required by the Cu CMP process. A new method for the planarisation length monitoring (step polish response) shows also significant differences in planarisation length (PL) by the polish of copper with slurries composed of these new particles. INTRODUCTION Due to the increasing demands in lithography, high end microelectronic processes require a continuously growing degree of planarisation. This fact in combination with an extension of the multitude of materials to be processed, created a need to design polishing slurries to meet very specific properties with respect to removal rate, selectivity and surface quality. Within the CMP for the local and global planarisation of the wafer surface, a combination of chemical and mechanical interactions are taking place. The slurry includes the acting chemistry as well as the physical constituent, the abrasive. The widely accepted general model mechanism for the effective planarisation at CMP consists of a 2-step process [1-3]. In the first step, the surface of the polished material reacts with the active chemical species of the slurry and forms a chemically altered surface layer. In the second step the altered surface layer is then removed by the mechanical abrasion. To continue the material transport, the abraded particles need to dissolve in the bulk of the slurry. The speed of reaction in the first step depends among other factors on the concentration of the reaction species, the temperature, and the mass transfer. The mechanical removal of this altered surface depends on the mechanical properties of the abrasive and pad, the polishing parameter and the bond strength of the altered layer to the subsurface. In this work, different abrasive dispersions prepared by DEGUSSA AG were used to assemble slurry formulations with constant pH value and constant additives like the complexing agent and
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oxidizer. These slurries were applied to a Cu CMP process. H2O2 was chosen as oxidizer and glycin as complexing agent. The pH value was adjusted to 4. This investigation enables an assessment of the contribu
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