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 μm. 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⁺-drain region does not always occur at the edge, independent of the isolation technology used