Physical meaning of /spl sigma/ value estimated with V/sub TH/-mismatch evaluation circuit

A new test chip is developed for clarifying the quantity corresponding to the standard deviation of the threshold voltage, /spl sigma//sub TC/, which is extracted using the test circuit proposed previously (Terada, K. and Eimitsu, M., Proc. IEEE Int. Conf. on Microelectronic Test Structures, p.227-31, 2003; Terada and Fukeda, K., Proc. IEEE Int. Conf. on Microelectronics Test Structure, p.155-59, 2004). Comparing /spl sigma//sub TC/ with the standard deviation calculated from the many data for individual MOSFETs, it is considered that /spl sigma//sub TC/ is a good approximation to the standard deviation of the threshold voltage.