Particles are transferred to wafer surfaces during application of spin-on dielectrics (SOD). Excessive particle levels on wafers are known to reduce device yield. Separate instruments using laser-light scattering techniques are used to assess liquid-born particles in SOD precursors and particles transferred to wafer surfaces in SOD processes. Experiment shows that, based on the particle concentration in the liquid, the number of liquid-borne particles dispensed onto the wafer is significantly larger than the number of particles measured on the wafer after SOD deposition. In experiments the obvious correlations expected between liquid-borne particle concentrations and wafer particle counts were not observed for the magnitude of liquid-borne particle concentrations commonly associated with modern VLSI device production. Two models are proposed to explain these observations. The models estimate the liquid-to-wafer particle transfer based on the liquid- borne particle concentration and the solids transferred either as a percent of total solids or as a percent of total volume. The models estimate that the number of particles transferred from even relatively high particle count spin-on dielectric liquid precursors challenge the measurement sensitivity/capability of the wafer surface scanning inspection station.
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