The sub-14 nm technology nodes of integrated circuits require metal components of ultrathin linewidths. The chemical mechanical planarization (CMP) protocols needed to process such structures are associated with several challenges, one of which is to design/screen slurry formulations required to address both the scaling and the nontraditional metal chemistries of these structures. Laboratory scale tribo-electrochemical techniques serve as a cost-effective yet comprehensive means to aid these tasks, and the present work focuses on further quantifying this approach with an alkaline slurry formulation designed to planarize Co diffusion barriers for Cu lines. The CMP strategy uses controlled corrosion in a (potentially abrasive-free) slurry of potassium acetate, hydrogen peroxide, and benzotriazole. The tribo-electrochemical experiments involve open circuit potential transients, current interruption, and potentiodynamic polarization. Material removal rates, normalized with respect to the polisher parameters are analyzed as specific wear rates to quantitatively probe the chemical aspects of CMP. The slurry functions necessary to control galvanic corrosion and CMP selectivity of Co are investigated. The necessity for incorporating tribo-control in these measurements is demonstrated by showing how the results obtained with stationary metal samples could result in misleading conclusions about the galvanic corrosion rates.
The sub-10 nm technology node has introduced significant chemical complexities in the associated processing steps of chemical mechanical planarization (CMP), and this has correspondingly convoluted the post-CMP cleaning (PCMPC) protocols. Focusing on selected cleaning chemistries, the present work demonstrates an in-situ tribo-electrochemical approach to developing fundamental knowledge of the PCMPC mechanisms for such systems. As model samples, the experiments use cobalt and copper thin films, deposited on wafer coupons, and treated in an alkaline CMP solution of acetate, H2O2 and benzotriazole. These samples are subsequently studied in an alkaline PCMPC solution of oxalic acid, designed for cleaning both Co and Cu. The surface cleaning characteristics of the metals are assessed by tribo-electrochemical measurements in the presence of mechanical brushing with a commercial rotary brush for PCMPC. The tribo-electrochemical parameters of the PCMPC-active brushed wafer regions are extracted from the recorded data to determine the cleaning mechanisms. Open circuit potential and voltammetric measurements indicate that oxalate ions serve to remove the CMP residues, Co(OH)2 and Cu-oxides from Co and Cu surfaces, respectively, in the forms of oxalate complexes. The residue removal efficiencies, measured by ex-situ impedance spectroscopy, are found in the 85–89% range for both Co and C
Due to its notable retention of electrical conductivity in nanoscale features, cobalt is a leading material candidate for diffusion barriers in the sub-14 nm node copper interconnects. In this application, Co also facilitates high aspect ratio gap-filling by serving as a substrate for direct electrochemical deposition (ECD) of Cu. However, the Co-Cu ECD system is associated with several technical challenges, which include dissolution of Cu seeds (and Co) in conventional acidic baths, interference of hydrogen evolution, and solution-sensitive nucleation barriers. We investigate here this ECD system by using pulsed galvanostatic ECD in a neutral plating bath of CuSO 4 , with in situ electroless deposition of Cu seeds. Both seeding and ECD of Cu are enhanced with the use of a carbon based catalytic activator. These observations are explained in terms of a proposed mixed-potential mechanism. Nucleation of the ECD-Cu is detected with voltammetry, and further quantified as an instantaneous step by measuring the associated kinetic parameters with chronoamperometry. Spatially uniform layers of pulse-deposited Cu on Co are detected by electron microscopy, and the deposition rates are determined using energy dispersed X-Ray spectroscopy. Corrosion tests performed in a glycine-based solution for Cu planarization confirm the general CMP compatible electrochemistry of the ECD-Cu.
The determination of phenols based upon coupling with 4‐aminophenazone in the presence of an alkaline oxidising agent has been examined. The importance of pH has been studied and a suitable buffering agent has been recommended. The reactivity of many phenols of pharmaceutical interest has been investigated and the application of the method to a number of pharmaceutical preparations is described.
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