US Patent 10551254 Approach to measuring strain effects using ring oscillators

A ring oscillator system for characterizing substrate strain including, a substrate including a through-substrate-via, at least two ring oscillators, wherein a first ring oscillator is closer to the through-substrate-via than a second ring oscillator, and a logic difference circuit that is configured to receive an input from at least the first ring oscillator and the second ring oscillator, and detect a difference between the signal frequency of the first ring oscillator and the signal frequency of the second ring oscillator.