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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]

Cobalt (Co) has been applied as one of the most promising candidates of barrier metals for copper (Cu) interconnects. The present work describes the static etching and chemical mechanical polishing process of Cu and Co, which were conducted by potassium persulfate (K2S2O8) as an oxidizer at various pH values. It was found that compared with the conventional oxidizer hydrogen peroxide (H2O2)-based slurries, the K2S2O8-based slurries exhibited a relatively high Co removal rate, as well as the diminished particulate contamination and excellent post-etching morphology. A slurry consisting of 3 vol% colloidal silica, 10 mM K2S2O8, and 5 mM benzotriazole (BTA) produced a Co removal rate of ~ 127 Å/min at pH 10, along with a removal rate selectivity of ~ 1 between Cu and Co films. Based on the data of X-ray photoelectron spectroscopy, scanning electron microscopy, and nano-scratch depth tests, the interplaying mechanisms of chemical and mechanical on Cu and Co removal rates in K2S2O8-based slurries were investigated. [ABSTRACT FROM AUTHOR]

Cobalt (Co) with its low resistivity, superior adhesion property, and void-free seamless fill ability, pledges to transform the landscape of integrated circuits in many areas, especially in interconnects and logic contacts. The present work describes the selection and optimization process of the complexing agent and inhibitor in chemical mechanical polishing barrier slurries relevant for heterogeneous materials of Co interconnects. An alkaline colloidal silica based slurry has been proposed, consisting of 0.5 wt% hydrogen peroxide, 5 mM dipotassium ethylenediaminetetraacetic acid (EDTA-2K), 13 mM potassium oleate (PO) and producing a Co removal rate of 45.6 Å/min, along with an appropriate removal rate selectivity between oxide dielectric, barrier layer and Co, which reaches above ∼ 2:1:1. Furthermore, synergetic effects of the oxidizer, complexing agent EDTA-2K and inhibitor PO on the Co CMP process have been investigated systematically by several analytical techniques, including electrochemical analysis, X-ray photoelectron spectroscopy survey, and adsorption isotherm characterization. The role of EDTA-2K affecting SERs and MRRs embodies in its strong complexing ability by dissociating to full deprotonated EDTA ion and then reacting with Co to produce very stable chelate Co(Ⅱ)EDTA. Moreover, the effect of inhibitor PO has a critical point. With the addition of PO at a low concentration, an effective passivation layer could be formed on Co surfaces spontaneously via chemisorption, protecting Co from severe pitting corrosion. While in case of PO at high concentration, Co(Ⅱ)PO ligand will be generated, reducing the stability of the original PO-Co passive layer and providing paths for complexing agent EDTA-2K to produce Co(Ⅱ)EDTA chelate. [ABSTRACT FROM AUTHOR]

When the feature size of integrated circuit continues to shrink below 14 nm, ruthenium (Ru) has become one of the most promising candidates for the application of novel barrier layer. To reveal the material removal mechanism of Ru during chemical mechanical polishing (CMP), surface characteristics of Ru in KIO 4 -based slurry were investigated. The corrosion behavior of ruthenium was measured by the surface chemistry and morphology analysis. Then the mechanical properties of the passivated/corroded surface were evaluated by AES and tribocorrosion experiments. CMP experiments were carried out to make clear the effects of surface property during polishing. It was found that the Ru surface chemistry and mechanical properties vary obviously as a function of slurry pH. In neutral slurries, the Ru surface is covered with RuO 2 ·2H 2 O/RuO 3 inhomogeneous passivation films, with the highest material removal rate obtained during the CMP process. It could be concluded that the material removal mechanism largely depends on the slurry pH values. In near neutral slurries, Ru is passivated with thick and heterogeneous oxides film, which proves the easiest to be mechanically removed during polishing. The weak alkaline slurry is preferred in order to achieve desirable polishing rate as well as avoid the formation of toxic RuO 4 . [ABSTRACT FROM AUTHOR]