Starting from a simple model of the distributions of charge created in an insulator by bombardment with electrons, the components of the electric field are evaluated by using Maxwell’s equations and image effects. The results are applied to the most common experimental situations: a semi‐infinite sample (i) bounded by a vacuum or (ii) covered by a conducting film, and a sample in the form of a film (iii) unsupported or (iv) covering a conducting substrate. The results are compared to some experimental data concerning, for instance, electromigration and electron‐stimulated desorption. In surface analysis the decay of the Auger signal from ions of opposite charges and the opposite behavior of ions of the same charge are explained. Similar effects observed in electron‐probe microanalysis of glasses are also elucidated. The results concern scanning electron microscopy, transmission electron microscopy, and electron‐beam lithography applied to biological objects, polymers, ceramics, minerals, glasses, and electronic devices. With slight modifications, the same model can be applied to cases of irradiation with ions or x rays. The evolution of the trapped charges with time is suggested, and the need to indicate the electric parameters (e and γ) of the investigated samples is outlined.

Some considerations on the electric field induced in insulators by electron bombardment

Electron beam damage in Auger electron spectroscopy

Safe and reliable design of MEMS components requires a statistical description of the material properties that are associated with failure. To this end, a series of microscale tensile tests was performed on polysilicon MEMS structures fabricated using Sandia National Laboratories' SUMMiT Vtrade process. Tensile bars were fabricated from each of the four freestanding polysilicon layers, with gage lengths ranging from 30 to 3750 mum. A two-parameter Weibull distribution appeared to adequately characterize the observed tensile strength distributions. The strength distribution was found to be dependent on the length of the tensile structures, as expected by the Weibull size effect, and unexpectedly strongly dependent on the layer from which the tensile bar was constructed. Specifically, the topmost polysilicon layer in the deposition process (poly4) was more than twice the strength of the bottom freestanding polysilicon layer (poly1). The mechanistic source of this layer-dependent strength appears to originate, at least in part, from process-dependent surface roughness, although other factors such as layer-dependent variations in microstructure, residual stress, and doping are also considered. A fracture mechanics analysis of the strength distributions suggests that the size of the critical flaws is in the vicinity from 50 to 150 nm. Fractography revealed crack origins along the sidewalls, corners, and top surfaces. Weibull strength distributions were also established at elevated temperatures: 200, 400, 600, and 800 degC in air and nitrogen environments. These results revealed the onset of ductility and reduction in strength at elevated temperatures: at 600 degC strength was less than 40% of the room temperature value. Most of the strength was regained if the material was tested at room temperature after a high-temperature exposure. In the discussion, we briefly review concepts for incorporating these observed strength distributions into probabilistic safe design of MEMS components

Strength Distributions in Polycrystalline Silicon MEMS

Techniques for elemental composition profiling in thin films

This paper reviews the application of Auger Electron Spectroscopy (AES) to the analysis of glass surfaces. Attention is drawn to experimental perturbations which may occur when analyzing glasses with absorbed and/or mobile species at the surface. Previous workers [1–4] have shown, for example, that mobile ions (e.g. Na) are very difficult to measure in glasses due to their migration under the electron beam. Special techniques developed to permit the measurement of mobile ions are discussed, and some recent applications of AES in current research at the University of Florida are presented.

Glass surface analysis by Auger Electron Spectroscopy

Auger analysis of SiO2 films thermally grown in O2 in the presence of HCl or Cl2 shows that the incorporated Cl is unstable during the measurement. Cl profiling and mass‐spectrometric sampling indicate that ionized Cl is transported in the electric field to the vacuum‐oxide interface where it is desorbed by high‐energy electrons. This instability restricts the usefulness of the Auger technique.

Auger analysis of chlorine in ``HCl‐ or Cl2‐grown'' SiO2 films

Phosphorus redistribution during thermal oxidation of degenerately doped silicon was investigated using Auger electron spectroscopy and ellipsometry. Concentration profiles were determined with a combination of chemical and sputter etching techniques. A substantial phosphorus pileup was observed in the oxide in a thin layer near the ellipsometrically determined Si–SiO2 interface. Calibrated against standards of known concentration, this layer was found to contain ∼2×1021 phosphorus atoms/cm3, independent of the oxidation temperature between 850 and 1000 °C.

Auger and ellipsometric study of phosphorus segregation in oxidized degenerate silicon

Phosphorus redistribution during thermal oxidation of degenerately doped silicon was investigated using Auger electron spectroscopy and ellipsometry. Concentration profiles were determined with a combination of chemical and sputter etching techniques. A substantial phosphorus pileup was observed in the oxide in a thin layer near the ellipsometrically determined Si–SiO2 interface. Calibrated against standards of known concentration, this layer was found to contain ~2×1021 phosphorus atoms/cm3, independent of the oxidation temperature between 850°C and 1000°C.

R. Hammer

Papers

Auger analysis of chlorine in ``HCl‐ or Cl2‐grown'' SiO2 films

Auger and ellipsometric study of phosphorus segregation in oxidized degenerate silicon

Auger and Ellipsometric Study of Phosphorus Segregation in Oxidized Degenerate Silicon