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The eddy-current method has been employed to realize the real-time measurement of thickness distribution and polishing endpoint detection of metal films during the metal chemical mechanical polishing (CMP) process. However, accuracy and sensitivity in thickness measurement can be significantly impacted by a variation in lift-off distance (about 3.5 mm), attributable to the progressive wear of the polishing pad. This paper proposes a novel triple-coil sensor system, integrated with an alternating-current bridge and designed for high-precision metal film thickness measurement. Subsequently, the measurement performance of the bridge output voltage was scrutinized using a theoretical model and a trans-dimensional finite element analysis model of electromagnetic fields and circuit coupling. The correlations between the amplitude, phase, and the ratio of the real part to the imaginary part of the output voltage, in context with film thickness, were determined at assorted excitation frequencies and lift-off distances. Both theoretical equations and simulation results affirmed that the phase and ratio were more resistant to lift-off distance variations than the amplitude, and a linear relationship was identified between the ratio and film thickness. Furthermore, the thickness measurement performance of the amplitude and phase, when the triple-coil was imbalanced, was dissected via numerical simulation. A profound understanding of the proposed system was provided and beneficial for the practical applications in real-time thickness measurements of metal films during the metal CMP process. [ABSTRACT FROM AUTHOR]

Cobalt (Co), with its low resistivity, superior adhesion property, and void-free seamless fill ability, is being considered by the industry as a promising candidate to replace the conventional tungsten contact plugs for middle-of-the-line and the wiring metal copper interconnects for back-end-of-the-line. Chemical mechanical polishing (CMP), whose demand is greatly increasing as device dimensions shrink to 7-nm node, has been recognized as one of the indispensable manufacturing approaches for the fabrication of multilevel metal interconnection structures. In addition to meeting the appropriate removal rates and removal selection of heterogeneous materials, excellent wafer surface quality and minimized residual particles, also have become the criteria in the developing process of CMP slurries for Co interconnects. This work investigates the optimization process of the final CMP step for Co interconnects by introducing surfactants in hydrogen peroxide based slurries. Various types of surfactants having different functional groups were employed and compared thoroughly by material removal rates (MRRs) and selectivity. The chemical and mechanical mechanisms of various surfactants during CMP process have been clearly revealed by various approaches, including polishing and static etching experiments, electrochemical analysis, tests of absolute zeta potentials, and particle sizes, as well as wafer surface energy measurements. Research results show that Co MRRs are directly correlated with functional groups of various surfactants. Moreover, absolute zeta potentials of abrasive particles can be deeply influenced by different types of surfactants, where the correlation between absolute zeta potentials and Co MRRs presents strong negative. On the other hand, direct positive correlation between oxide MRRs and particle sizes affected by corresponding surfactants can be summarized. Meanwhile, no obvious corresponding relationship between contact angles and MRRs was found, indicating MRRs were barely affected by wettability of wafer surfaces. At last, the selected surfactants were applied to 12-inch wafers for verification, including MRRs, removal selectivity, defects and surface roughness. Each of these surfactants could make Co and TEOS surface Ra maintain at around below 0.7 nm and 0.3 nm, with a number of residual particles lower than 600 particle/wafer. [ABSTRACT FROM AUTHOR]

Recently, the technology node shrunk below 7 nm and beyond; cobalt (Co) and its low resistivity, superior adhesion property, and excellent electro-migration performance pledge to transform the integrated circuits' landscape in several areas, especially in interconnects and logic contacts. The present work proposes a weakly alkaline polishing slurry for Co interconnects, mainly consisting of colloidal silica, hydrogen peroxide, glycine, and 1,2,4-triazole at pH 8.1. The feature of tunable high material removal rate (greater than 1000–2000 Å/min) and fitting removal selectivity (~ 160) between Co and oxide dielectric could be realized by a moderately variable concentration of glycine complexing agent. Moreover, several analytical techniques, including electrochemical analysis, X-ray photoelectron spectroscopy survey, and adsorption isotherm characterization, were used to understand the interaction mechanism during Co material removal process. The results reveal that 1,2,4-triazole could adsorb on the Co oxide layers via physisorption, achieving an inhibition effect to avoid Co excessive corrosion. Furthermore, the oxidization of hydrogen peroxide, the complexation of glycine zwitterions, and the abrasive mechanical action are critical to maintaining the appropriate material removal rate. Based on the results with research-level wafers, the optimized Co bulk slurry was ultimately applied to the production-level of Co and oxide dielectric wafers. The residual particle, haze condition, and surface profile after polishing have been researched simultaneously. [ABSTRACT FROM AUTHOR]

In this paper, the effect of slurry injection position on removal rate and nonuniformity was experimentally investigated on a 300-mm polisher developed by the authors, and the effect of slurry injection position on slurry fluid pressure distribution during polishing was also measured by a novel in situ fluid pressure measurement system integrated in the polisher. In situ pad conditioning was employed in all experiments. The results showed that removal rate, nonuniformity, and fluid pressure distribution were influenced dramatically by the slurry injection position. The slurry injection position determines the slurry distribution, and therefore, the removal rate profile and fluid pressure distribution were affected. [ABSTRACT FROM AUTHOR]