CHARACTERIZATION OF SEMIINSULATING POLYCRYSTALLINE SILICON PREPARED BY LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION

Abstract

We employed the multiple angle incident ellipsometer to study the growth mechanism and optical properties of semi-insulating polycrystalline silicon (SIPOS) films deposited by the low-pressure chemical vapor deposition (LPCVD) technique. A significant difference of the imaginary part of the refractive index between film at the edge and those in the central region of the wafer was observed. Our analyses showed that it was consistent with the N2O depletion model. This N2O depletion phenomenon was confirmed by Auger analysis. Moreover, we found that spatial N2O depletion at the edge of the wafer was greatly influenced by the flow rate of SiH4 to N2O gases. Excessively high N2O flow rate suppressed the silicon microcrystal resulting in a thinner SIPOS film.