RESUMEN
For successful size separation in biomedical applications, the filter used must meet several strict criteria. Not only must it have precisely-machined sub-100 nm pores (<5% variation), but it must also be able to handle large and small volumes with very high reduction ratios (>10(4)). In this paper, we will present a bulk-micromachined, direct-bonded silicon nanofilter that can remove particles as small as 44 nm. In doing so, we will describe the fabrication, the gas and liquid characterization, and the filtrations studies done on 44 nm and 100 nm beads.
RESUMEN
Calculated values of reflectance at normal incidence for thinly oxidized silicon wafers are presented. The calculations, which use published, experimentally derived optical constants, cover the spectral range from ultraviolet (0.38 microm) to near infrared (1.24 microm). Oxide thickness varied in 0.1-microm steps from 0 to 1 microm, the range of practical interest to technologists in silicon and integrated circuits. Reflectance curves are correlated with the interference color chart for oxidized silicon. Finally, the dependence of reflectance on oxide thickness at three common laser wavelengths is graphed, for those interested in the recently developed endpoint detection techniques of plasma etching.
RESUMEN
A reflectometer is described that extends the continuous measurement of the near-normal-incidence reflectance of solids to vacuum ultraviolet (vuv) wavelengths. Clean reflecting surfaces are achieved by in situ sample preparation and ultrahigh vacuum environment. The low intensity problem is solved with electronic lock-in amplification. The over-all instrument has an absolute error of reflectance of (DeltaR/R)(Absolute) = +/-0.03. The precision is estimated to be (DeltaR/R)(Relative) = +/-0.002 or better. The wavelength range of 1100 A to 7000 A is covered. Some representative results show that this design provides substantial improvement in sensitivity and resolution of vuv reflectance measurements.
