Channel-width measurements of LOCOS- and trench-isolated MOSFET's by photoemission

A nondestructive, accurate, and simple method has been developed to measure channel width in processed MOSFET's fabricated with LOCOS or trench isolation. The method is based on spectroscopic analysis of the light emitted from breakdown occurring in the reverse-biased drain region. A high-resolution microscope is used to observe the photoemitted light from CMOS devices with channel widths ranging from 10 to 0.2 /spl mu/m. The method is applicable to surface-channel n-MOSFET's fabricated with either isolation. For buried-channel p-MOSFET's, the method is not successful because reverse breakdown in the p/sup +/-drain region does not always occur at the edge, independent of the isolation technology used.< >