Nanoanalysis of semi-insulating polycrystalline silicon by high-spatial-resolution electron microscopy

Abstract

Semi-insulating polycrystalline silicon (SIPOS) has been used extensively as a passivating layer in highvoltage power devices and as the wide bandgap material in solar cells. Little information, however, is available on the nano-scale nature of oxygen distribution and its redistribution upon thermal annealing, and the rnicrostructural characteristics of SIPOS thin films. In the present study, the atomic structure of SIPOS layers on Si wafers was characterized by HREM and the oxygen content was quantitatively determined by nanospectroscopy.SIPOS films were chemical vapor deposited on Si {001} wafers from a preset mixture of SiH4 and N2O. Annealing was done in dry N2 at 900°C for 30 min. Cross-sectional TEM specimens were prepared from both as-deposited and annealed materials. HREM was done in an ISI-002B at 200kV. Nanospectroscopy was performed at 100kV in a Philips EM400ST/FEG microscope coupled to a Gatan parallel-detection EELS, with better than 3 nm spatial resolution.