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We examined the effect of the molecular weight of surfactants in ceria slurry during chemical mechanical polishing (CMP) for shallow trench isolation (STI). We found that for a surfactant with a higher molecular weight, the oxide removal rate decreased drastically as the surfactant concentration increased, but in the case of a lower molecular weight, it only slightly decreased. In addition, slurries whose surfactants had lower molecular weights maintained a higher nitride removal rate with increasing surfactant concentration. The results showed that the molecular weight and surfactant concentration have complex effects on the oxide removal rate and the oxide-to-nitride removal selectivity.

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The effects of the electrokinetic behavior of abrasive ceria particles suspended in an aqueous medium and the deposited plasma-enhanced tetraethylorthosilicate (PETEOS) and chemical vapor deposition (CVD) Si3N4 films on chemical mechanical planarization (CMP) for shallow trench isolation were investigated. The colloidal characteristics of ceria slurries, such as their stability and surface potential, in acidic, neutral, and alkaline suspensions were examined to determine the correlation between the colloidal properties of ceria slurry and CMP performance. The surface potentials of the ceria particles and the PETEOS and CVD Si3N4 films in an aqueous suspending medium were dependent on the pH of the suspending medium. The differences in surface charges of ceria particles and the PETEOS and CVD Si3N4 films have a profound effect on the removal rate and oxide-to-nitride selectivity of CMP performance.

A quantum wire-on-well (WoW) structure, taking advantage of the layer undulation of an InGaAs/GaAs/GaAsP superlattice grown on a vicinal substrate, was demonstrated to enhance the carrier collection from the confinement levels and extend the carrier lifetime terraces, whereas the growth on a substrate without miscut resulted in planar layers. The undulation was the most significant for InGaAs layers, forming periodically aligned InGaAs nanowires on planar wells, a wire-on-well structure. As for the photocurrent corresponding to the sub-bandgap range of GaAs, the light absorption by the WoW was extended to longer wavelengths and weakened as compared with the planar superlattice. Almost the same photocurrent was obtained for both the WoW and the planar superlattice. Open-circuit voltage for the WoW was not affected by the longerwavelength absorption edge, and the same value was obtained for the two structures. Furthermore, the superior carrier collection in the WoW, especially under forward biases, improved fill factor compared with the planer superlattice.