High resolution electron microscopic and spectroscopic characterization of semi-insulating polycrystalline silicon and its interface with single-crystal silicon

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Abstract
A combination of high resolution electron microscopy (HREM), electron energy loss spectroscopy (EELS), energy dispersive x‐ray analysis (EDXA), and scanning transmission electron microscopy (STEM) techniques has been employed to characterize the structure and composition of vapor‐deposited thin films of semi‐insulating polycrystalline silicon (SIPOS) and their interfaces with Si. SIPOS layers containing ∼30 at. % of oxygen are amorphous when deposited at Si substrate temperature of 625 °C. Upon annealing at 900 °C in N2 for 30 min, Si crystallites up to ∼100 Å in size appear throughout the SIPOS layer, the microstructure of which appears to be a dispersion of Si crystallites in an amorphous matrix. The plasmon‐loss spectra show a characteristic energy for each material: 16.7 eV for Si, 17.6 eV for SIPOS, and 23.2 eV for SiO2, which correlate empirically with increasing oxygen content in these materials. A combination of HREM and STEM revealed the existence of a 25–30‐Å native oxide layer between the SIPOS and Si substrate. This native oxide yields a plasmon loss at 22 eV using a 10‐Å probe in the STEM.

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