Oxidation states in scanning-probe-induced Si₃N₄ to SiO_x conversion studied by scanning photoemission microscopy

The biased conductive probe of an atomic force microscope can induce local oxidation in ambience for converting silicon nitride films to silicon oxides with high reaction rate. Spatially resolved photoemission analysis with submicron resolution has been utilized to study the oxidation states of converted silicon oxide patterns in comparison with the surrounding Si₃N₄ layer. The core level shift of the Si 2p photoelectron peak and the spectral features in the valence band reveal a complete conversion of silicon nitride to silicon oxide at a bias voltage of 10 V, with no remaining nitrogen left. The major oxide is SiO₂. The observed oxidation states of Si⁴⁺, Si³⁺, and Si²⁺ show a gradient depth distribution indicating excess silicon in the layer. © 2001 American Institute of Physics.