Patent ID: 6239591
Filing Date: 2001-05-29
Classification: H01L

Abstract:
Method for measuring SOI floating-body time-delay hysteresis effects of a wafer process, the method comprising:generating a pulse having a pulse width equal to the delay of a transition through a multi-stage delay chain formed in said wafer, wherein the delay chain has been in a static condition for a substantial length of time, said pulse width representing a delay time corresponding to a first switch delay;for a time duration equal to said pulse width, counting a number of oscillations from a ring oscillator constructed of the same individual stages that are used in said multi-stage delay chain and operating in steady-state condition, said oscillations of said ring oscillator comprising pulses with each pulse representing an average steady state stage delay time for said ring oscillator, said number of oscillations being proportional to a ratio of said first switch time-delay to said average ring oscillator steady state time-delay; andcomparing the number of oscillations with an expected value, wherein a difference between a measured number of oscillations and said expected value represents deviations in said time-delay hysteresis, said deviations in said time-delay hysteresis correlating to variations in said wafer process.