Transient Current Testing of Gate-Oxide Shorts in CMOS

We propose a method for testing gate-oxide shorts due to pinhole defects in the gate oxide of CMOS circuits using the transient power supply current, iDDT. The method is based on switching the CMOS gate, monitoring the peak value of the transient current and comparing it to that of the defect-free gate. If the magnitude of the peak current is higher than a predetermined threshold, a defect is inferred. The MOS transistor is modeled using the nonlinear split model. We take into consideration the different locations and sizes of the short. Simulation results show a high rate of detection for gate-oxide shorts that cannot be otherwise detected using traditional testing techniques. We also show that by using a normalization procedure, the defects can be detected with a single threshold setup in the presence of leakage and process variations that normally hinder the detection capability of current-based testing techniques.