Fast Embedded Characterization of FEOL Variations in MOS Devices

The objective of this paper is to present a test chip based on embedded ring oscillators (RO) measurement with its associated extraction algorithm to characterize length and width variations and to discriminate them from others FEOL variations. A brief overview of the structure, designed in a ST-Microelectronics 90nm technology, is given with emphasis on the ROs geometry with their biasing conditions and the measurement circuit. Comparison of simulated values versus estimated ones is given and confirms the ability of the structure to characterize FEOL variations. MOS width and length are well estimated regardless the others FEOL deviations that can be also detected.