The large particle count ͑LPC͒ of fumed silica slurries was evaluated and correlated with scratch counts created on SiO 2 films by table-top, chemical-mechanical planarization ͑CMP͒. Particle sizing results obtained by static light scattering, capillary hydrodynamic fractionation, and dual-sensor single particle optical sensing ͑SPOS͒ pointed to the latter as the superior method for quantitative analyses of the LPC. Dual-sensor SPOS is a new technique that determines the LPC on a silica sphere-equivalent, light-scattering diameter scale for particles as small as 0.469 m. LPC measurements used in combination with dark-field optical microscopy for scratch metrology afforded linear correlations between scratch counts and the LPC. Particles producing scratches had silica sphere-equivalent, light-scattering diameters exceeding 0.68 m. Inclusion of these particles in the LPC produced a two-fold increase in the number of scratch-forming particles in the correlation relative to correlations generated via single-sensor SPOS measurements of LPC. Experimental uncertainty in scratch counts limited the correlation as a scratch predictor. Slurries differing in LPC by a minimum of 1.8 ϫ 10 5 particles/g slurry had statistically different predicted scratch counts at the 95% confidence level. Additional method development is needed to extend LPC-based scratch prediction to other CMP processes producing scratch defects.Among the set of key criteria defining the limits of microelectronic device fabrication, the reduction of surface defects assumes special prominence. It is well established 1 that surface defects on a microelectronic device degrade device performance. A variety of defect types, including delaminated film interfaces, pits, scratches, and chemical and physical changes in film structures, have been identified as the products of surface-damaging events during device fabrication. 1 Given the overwhelming need to reduce the size of microelectronic devices in order to produce faster and more powerful commercial microprocessors, strategies for reducing all types of surface defects have become a critical element of the fabrication processes used by the microelectronic device industry.Reaching the desired state of minimized surface defects on microelectronic devices begins with the recognition that a principal source of surface defects in device fabrication processes is surface polishing and planarization afforded by chemical-mechanical planarization ͑CMP͒. 2,3 The current paradigm of CMP-driven defect generation attributes the creation of defects to the mechanical action of the largest diameter particles in a CMP slurry. 4-6 Although a detailed mechanistic understanding of this process remains elusive, research efforts have sparked the development of many new analytical methods and techniques for the characterization of the abrasive particles and other consumables in CMP slurries. 7 A key analytical metric, widely applied to predict the defect creation potential of CMP slurries, is the large particle count ͑LPC͒ for the slur...
Transmission electron microscopy has been used to evaluate the primary particle size distributions and aggregate structure of a fumed silica sample. The primary particle size distribution within an individual aggregate is narrow, with a geometric standard deviation of ∼1.2. The distributions of maximum diameters, projected areas, and average primary particle diameters were all skewed, and all were better described by a log-normal distribution than a normal distribution. The data confirmed the fractal description of the fumed silica aggregate structure, with a mass fractal dimension of 1.86. The fractal prefactor or lacunarity was evaluated from the aggregate volume and the maximum particle dimension, and found to have a value of 0.83 for this sample.
This work reviews the mechanical properties and fracture mechanics of materials important in the manufacture of multilayer interconnects on silicon chips in order to understand surface damage caused during chemical mechanical polishing (CMP). It 2 gives an explanation for chatter marks, surface flaking in interlayer dielectric material (ILD) and rolling indenter and plastic plow lines in copper on the wafer surface during CMP of silicon chips.
Disc centrifuge photosedimentometry (DCP) with fluids of different densities is used to simultaneously determine the particle size and effective density of spherical silica particles. Incorporation of a calibrated infrared pyrometer into a DCP instrument is shown to enhance the measurement capability of the DCP technique by correcting for the temperature dependence of the spin fluid's density and viscosity. Advantages of absolute DCP determinations for size and density analysis relative to standardized DCP measurements include the elimination of instrument standardization with a particle of known density and measurements or estimation of the effective particle density. The reliability of diameter determinations provided by absolute DCP was confirmed using silica particles with nominal diameters ranging from 250 to 700 nm by comparison of these analyses with a diameter determination by transmission electron microscopy for silica particle size standards. Effective densities determined by absolute DCP for the silica particles ranged from 2.02 to 2.34 g/cm(3). These findings indicate that the silica particles have little or no porosity. The reported characterization of colloidal silica using absolute DCP suggests applicability of the technique to a variety of particle types including colloidal materials other than silica, core-shell particles, compositionally heterogeneous mixtures of nanoparticles, and irregularly shaped, structured colloids.
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