Photothermal wave imaging of metal-oxide-semiconductor field-effect transistor structures

A photothermal wave imager has been assembled and used to generate thermal-wave images of an active metal-oxide-semiconductor field-effect and related inactive microelectronic structure fabricated on a silicon chip. The imager, which monitors the thermoelastic surface deformation due to absorption of a highly focused, intensity-modulated heating laser beam, has proven to be capable of producing images of subsurface features related to processing steps (thermal-wave depth profiling) at open circuit, as well as current flow sensitive images related to electronic processes in the active transistor (plasma-wave depth profiling).