Effectiveness evaluation of the TSV fault detection method using ring oscillators

During the 3D Stacked ICs fabrication, various defects in TSVs could come up, resulting both in performance and reliability reduction. These defects could produce serious problems in the early stages of fabrication. The situation gets more difficult because there is limited test access to TSVs, before and after wafer thinning. An analysis of effectiveness on oscillation-based pre-bond TSV test methods, based on frequency difference between a fault-free and a defective TSV, is presented. TSVs are embedded, modeled as RC elements, in a ring oscillator and the frequency is measured. When a defective TSV is inserted to the ring oscillator, it results to variations in the frequency of the circuit. The alteration of the frequency can lead us to the detection of leakage and resistive open faults. Many Monte Carlo simulations are used in each case (fault-free or faulty), to verify the robustness of the test. 65nm CMOS technology models were used for the design of the ring oscillators.