The fabrication of nanometer-scale side-gated silicon field effect transistors using an atomic force microscope is reported. The probe tip was used to define nanometer-scale source, gate, and drain patterns by the local anodic oxidation of a passivated silicon (100) surface. These thin oxide patterns were used as etch masks for selective etching of the silicon to form the finished devices. Devices with critical features as small as 30 nm have been fabricated with this technique.

A technique is presented for fabricating Si nanostructures with a scanning tunneling microscope operated in air. The process involves the direct chemical modification of a H-passivated Si(100) surface and a subsequent liquid etch. The chemically modified portions of the surface can withstand a deep (≳100 nm) liquid etch of the unmodified regions with no etch degradation of the modified surface. At a write speed of 1–10 μm/s, large-area (50 μm×50 μm) patterns with lateral feature sizes ∼25 nm are reliably fabricated.

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Spectroscopic ellipsometry was used to determine the density of oxides thermally grown on Si substrates as a function of the oxidation temperature, and the time and temperature of postoxidation anneals. All the oxides were found to be denser than fused silica. The density of the as-grown oxides was found to decrease as the growth temperature was increased. Postoxidation anneals were found to reduce the oxide density; high temperature or long-time anneals caused the greatest reduction in density. Holes alone, or holes and electrons, were injected into the oxides by irradiating with vacuum ultraviolet light or x rays under electric field bias. Using capacitance–voltage measurements, it was found that low-density oxides trap charge more efficiently than high-density oxides. Electron spin resonance measurements indicated that, for most of these oxides, the number of paramagnetic defects was substantially smaller than the number of trapped charges. It is hypothesized that the additional, nonparamagnetic, charge is in the form of protons trapped near network oxygen atoms that have large Si–O–Si bond angles. The number of these large-angle bonds in the near-interfacial oxide increases as the oxide density decreases, explaining the observed correlation between the charge trapping and the oxide density.

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It is shown that spectroscopic ellipsometry (SE) studies followed by the regression analysis of the SE data can yield information nondestructively and in a nonperturbing manner on the depth profile of multilayer structure; such as (i) quantitative information on the thickness and the dielectric function of each layer, (ii) the structure (whether crystalline or amorphous) as well as the degree of crystallinity of each layer, (iii) characterization of the oxide layer if present on the specimen, and (iv) microroughness of the surface, if present. Furthermore, it is shown that these results are in excellent agreement with the results obtained on the same specimens using cross-section transmission electron microscopy.

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