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.

Through chemical mechanical polishing (CMP) tests using polycrystalline silicon (polysilicon) and oxide blanket film wafers, the effects of alkaline agents added to colloidal silica slurries were investigated. With increasing concentration of the alkaline agent, a decreasing trend after an initial increase in the polysilicon removal rate was found, along with a low oxide removal rate, enabling high selectivity. The surface roughness similarly became worse and then better with increasing concentration of the alkaline agent. The results suggest a mechanism in which hydroxide bonds to the Si surface of the abrasives in the slurry and OH- attaches to the polysilicon surface. The silanol group induces high polarization and thus weakens the Si–Si back bonds. These results can be qualitatively explained in terms of the chemical reaction between the polysilicon surface and the alkaline agent in the slurry, according to the hydrophobicity and hydrophylicity as indicated by contact angle measurements.

No abstract

The propagation of a plane electromagnetic wave through a Lorentz plasma in a sheared magnetic field is considered. The characteristic waves in a uniformly sheared, but otherwise homogeneous, medium are found, and their properties presented graphically. Some effects introduced by the presence of shear are investigated by means of elementary applications of the uniform-shear theory. By suggested extensions of the analysis, refinements may be made in the interpretation of microwave diagnostic experiments with controlled-fusion containment devices having complicated sheared fields. . I N T R O D U C T I O NA COMMON refinement to the Appleton-Hartree theory of electromagnetic wave propagation in a magnetized (anisotropic) plasma is consideration of spatial inhomogeneity of the plasma electron density (BACHYNSKI, 1960). In this paper, we investigate another type of inhomogeneity, namely, spatial variation of the orientation of the magnetic field. The problem is suggested by the importance of sheared magnetic fields in the plasma containment devices of controlled fusion research, such as the diffuse pinch, the multipolar Stellarator, and the Ioffe stabilized mirror configuration.Initially assuming a simple model for the sheared field, we derive a dielectric tensor and the resulting wave equations. Then with further simplifying assumptions, we find the characteristic waves in a 'uniform' sheared medium. The general problem, for an arbitrarily complicated model of magnetic field configuration and electron density profile, may be set u p by a straightforward extension of the analysis given. 5617

No abstract