Slurries used for chemical mechanical planarization (CMP) of copper generally contain certain dissolution inhibiting chemicals that help to improve the planarization efficiency (PE) of CMP by selective removal of Cu from protrusion regions of patterned wafers. Benzotriazole (BTAH) is a widely employed inhibitor in this category, but its use often leads to defects on the finished surface by generating insoluble debris on the polishing pad. We show how this problem can be addressed by using an environmentally friendly surfactant, ammonium dodecyl sulfate (ADS), as a primary dissolution inhibitor of Cu in the CMP slurry. Incorporation of ADS in the CMP slurry allows for a substantial reduction in the use of defect-causing BTAH in the slurry. The mixed inhibitors exhibit excellent performance both in suppressing Cu dissolution and in enhancing the PE of CMP. The individual and synergistic effects of ADS and BTAH on Cu dissolution were examined using a background slurry of 1wt% glycine, 5wt% normalH2normalO2 , and 3wt% fumed silica. Incorporation of 3mMADS+0.5mMBTA in this slurry yielded significantly lower dissolution rates ( ≤1nm∕min at 40°C ) of Cu than that (∼40nm∕min) obtained with 10mM BTAH. The PE of CMP, evaluated using 15μm wide and 5000Å deep topographies on a Cu wafer, also is considerably higher (97%) for the ADS-BTAH mixed slurry than that (75%) for the slurry containing 10mM BTA without ADS.

An important component of the slurries used in chemical mechanical planarization (CMP) is an appropriately chosen corrosion/dissolution inhibitor, which facilitates selective material removal from protrusions while protecting recessed regions of the surface. The present work demonstrates the utility of two environmentally benign anionic surfactants, sodium dodecyl sulfate (SDS) and ammonium dodecyl sulfate (ADS) as dissolution inhibitors. Using a standard slurry (1 wt% glycine with 5 wt% H 2 O 2 at pH ‫ס‬ 4.0) typically used for Cu CMP and combining measurements of open circuit potentials and contact angles with those of Cu removal rates, we show that both SDS and ADS suppress chemical dissolution and polish rates of Cu. The dissolution inhibition efficiencies of ADS and SDS measured in these experiments are found to be superior to those of benzotriazole (BTA), a traditional inhibiting agent used for copper CMP.

Electrochemical mechanical planarization ͑ECMP͒ is designed for low-pressure processing of 65 nm and smaller semiconductor device structures using electrochemical reactions in abrasive-free electrolytes. In ECMP, a corrosion inhibitor facilitates uniform surface planarization through selective material removal from protrusions under voltage activation while protecting the recessed areas. We demonstrate here that ammonium dodecyl sulfate ͑ADS͒, an environmentally safe surfactant, can be utilized for this application in ECMP of copper. Using an acidic electrolyte of glycine and H 2 O 2 , and small Cu disks, we show that the corrosion inhibition efficiency of ADS is superior to that of benzotriazole.Copper damascene structures in the fabrication of integrated circuits are processed by chemical mechanical planarization ͑CMP͒, and a rapidly emerging extension of CMP is electrochemical mechanical planarization ͑ECMP͒. 1-5 ECMP utilizes voltage-activated anodic dissolution for material removal, where mechanical polishing can be performed at Ͻ1 psi applied pressure for minor leveling of topographies in nearly or completely abrasive-free electrolytes. 4,5 This low-pressure ͑and possibly abrasive-free͒ capability of ECMP is particularly attractive for processing 65 nm and smaller structures that contain mechanically fragile, porous low-permittivity materials. 1,5 ECMP involves precisely controlled ͑not necessarily maximized͒ material removal through simple adjustment of electrochemical variables. 4 Achieving uniform across-wafer planarization in this technique, however, relies on controlled and repetitive formation and subsequent removal of a thin passivating layer on the sample surface. This passive film protects the recessed areas of the surface from electrochemical corrosion, while protrusions on the same surface are planarized by the combined mechanical abrasion and electrochemical reactions. Selection of an appropriate corrosion inhibitor is difficult because the commonly used corrosion protective organics often produce unavoidable debris during polishing, eventually causing scratches and defects on the wafer surface. 1 In the present work, we demonstrate that ammonium dodecyl sulfate ͑ADS͒, an environmentally friendly surfactant, can be used as an efficient corrosion inhibitor for ECMP of Cu in hydrogen peroxide/ glycine solutions. 3,7 We use a standard acidic ͑pH 4.0͒ solution of Cu CMP/ECMP, containing 1 wt % glycine ͑complexing agent͒ and 5 wt % H 2 O 2 ͑oxidizer͒, with and without ADS ͑corrosion inhibitor͒. We obtain the corrosion inhibition efficiency of ADS at equilibrium ͑zero-current condition of CMP͒ by using potentiodynamic polarization measurements using small Cu disk samples. The inhibition efficiency of ADS against electrochemical corrosion ͑for ECMP͒ is measured in the presence of moderate and strong anodic voltage activation. The corrosion parameters for ADS are compared with those for benzotriazole ͑BTA͒, a conventional corrosion inhibitor for Cu. 8,9 This comparison is further extended to the case of...

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A new parallel-type gripper mechanism is proposed in this work. This device has a parallelogramic platform that can be flexibly folded. Therefore, this mechanism not only can be used to grasp an object having irregular shape or large volume, but also can be utilized as a micro-positioning device after grasping objects. Forward position analysis and platform kinematics are investigated to deal with motion tracking and force control. Kinematic optimization is performed to design a parallel-type gripping mechanism so that it can reach the specified workspace, span the given range of the specified configuration parameters, and generate a desired force to grasp an object. A pneumatic rotator is employed for actuation and a miniaturized proportional 4/3-way directional valve is specially developed to deal with feedback-based dynamic control. The proportional valve allows indirect force control by measuring the offset-load pressure raised by the contact between the grasped object and the parallel platform. In experimental work, the performance of the motion tracking and indirect force control has been shown to be successful.