Correlation of Defects on Dielectric Surfaces with Large Particle Counts in Chemical-Mechanical Planarization (CMP) Slur
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Correlation of Defects on Dielectric Surfaces with Large Particle Counts in Chemical-Mechanical Planarization (CMP) Slurries Using a New Single Particle Optical Sensing (SPOS) Technique Edward E. Remsen, Sriram P. Anjur, David Boldridge, Mungai Kamiti and Shoutian Li Cabot Microelectronic Corporation 870 North Commons Drive Aurora, IL 60504, U.S.A. ABSTRACT A dual-sensor single particle optical sensing method (SPOS) is described for the measurement of the large particle count (LPC) in fumed silica polishing slurries. LPC values were expressed on a silica sphere-equivalent diameter scale rather than a polystyrene latex-equivalent size basis. Linear correlations between LPC and scratch counts on SiO2 surface films for wafers polished under clean room and table-top CMP conditions are demonstrated. However, these correlations were obtained for a limited set of model slurries; and further investigation will be needed to assess the general applicability of dual-sensor SPOS for oxide scratch defect prediction in CMP slurries.
INTRODUCTION The creation of surface defects on a microelectronic device can profoundly degrade device performance [1]. A principal source of surface defects is the polishing and planarization afforded by chemical-mechanical planarization (CMP) [2,3]. An analytical metric, widely applied to predict the defect creation potential of CMP slurries is the LPC for the slurry [4,5]. The LPC is an estimate of the number (or mass) of particles present in the large particle tail of the slurry’s particle size distribution. In the present study a new SPOS technique incorporating dual optical sensors is employed in the analysis of LPC. The dual-sensor SPOS method measures the contribution to the LPC and the particle size distribution from particles smaller in size than the particles normally measured with established single-sensor SPOS techniques. This new approach is demonstrated in concert with the CMP of dielectric surfaces using table-top and clean room polishing tools. Polished wafers were analyzed to determine the number of surface defects (scratches). Demonstrated correlations of scratch counts with LPC measured using dual-sensor SPOS provide a new direction and analytical methodology for the further investigation of CMP-driven defect generation mechanisms.
EXPERIMENTAL DETAILS The LPC for particles in fumed silica CMP slurries with silica sphere-equivalent diameters greater than 0.469 µm was provided by dual-sensor SPOS measurements. A model AD-10300-001 SPOS instrument (Celerity Inc., Tualatin, OR), equipped with model LiQuilaz S03 and LiQuilaz S05 particle sensors (Particle Measurement Systems
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Inc., Boulder, CO) was employed. Particle size distributions for the slurries were characterized by static light scattering (model LA-910, Horiba Instruments Co., Irvine, CA) and capillary hydrodynamic fractionation (model CHDF2000, Matec Applied Sciences Inc., Northborough, MA). CMP conducted under clean room conditions employed an IPEC 472 polisher (Novellus Systems Inc., San Jose, CA) equippe
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