The need for a next-generation chemical mechanical polishing (CMP) slurry for copper planarization, to meet the requirements posed by advanced copper damascene processes, has led to the conception and development of a new type of slurry. The new “micelle slurry” is based on a mixture of surfactant and heteropolyacid, which takes the form of surfactant micelles enveloping the copper-reactive heteropolyacid. When used in the CMP process in place of conventional slurries, it effects copper planarization by a chemical mechanism with little or no mechanical abrasion. The mechanism enables a high rate of copper removal under low polishing pressures with minimal copper “dishing,” largely free from the scratching or erosion that may be encountered in CMP with conventional slurries due to their abrasive particle contents. These characteristics are advantageous for planarization of advanced copper damascene interconnects and particularly those including the relatively fragile low-k dielectrics. The micelle slurry also reduces the need for frequent dressing of foamed pads and enables a remarkably high rate of copper planarization with nonfoamed hard pads under low polishing pressures. It may therefore lengthen the pad service life and reduce the complexity and cost of CMP, particularly for copper damascene interconnects incorporating low-k dielectrics. © 2003 The Electrochemical Society. All rights reserved.

The effect of pad surface texture on dielectric and copper removal rates was studied theoretically and experimentally by investigating the fluid behavior of the slurry layer using methodologies similar to those found in tribological investigations of fluid bearings. It is shown that new nonfoamed hard plastic pads with intricate groove patterns are critical in modulating removal rates. Removal rate results of dielectric chemical mechanical polishing were in close agreement with model predictions for several of the groove designs tested. Combined patterns, consisting of spiral and logarithmic grooves, were shown to impact several key attributes of the dielectric and copper processes in terms of slurry retention, hydrodynamic pressure, tribological mechanism, and material removal rates.

The adhesion strength of copper layers on TaN barrier layers decreases from 19.5 to 10 gf with annealing at 400°C. A much lower stress layer can be obtained when a seed layer is deposited on a TaSiN barrier layer. The adhesion strength is as high as 35 gf and is not changed by annealing. The critical pressure for delamination at the barrier layer/low dielectric ͑͒ layer interface decreases from 350 to 200 g/cm 2 when is reduced from 3.3 to 2.7 in an SiOC interlayer. That is, better adhesion strength can be attained when an interlayer with a higher dielectric constant is used.

Spectral analysis of real-time friction data obtained during ILD CMP is used to elucidate the tribology of the process in terms of stick-slip phenomena. Fourier transform analysis is employed to quantify the total amount of mechanical interaction in the pad-slurry-wafer interface as a function of various IC-1000 pad surface textures, PL-4217 fumed silica concentrations, relative pad-wafer velocities and applied wafer pressures. A new parameter termed the ‘Interfacial Interaction Index’ (γ) is defined and determined empirically by integrating the amplitude of the force spectra over a wide range of frequencies. Values of γ extracted from individual force spectra are in qualitative agreement with the tribological information obtained in previous studies using Stribeck curve analysis. This new method is remarkable since it has the potential to eliminate having to perform a multitude of experiments needed for constructing and interpreting Stribeck curves. For a given tribological mechanism, analysis of the spectra for various types of pad textures indicates significant differences between the K-Grooved pad and other types of pads. A qualitative model relating the observed spectra to pad storage modulus is presented as a potential explanation for the above observation.