A test structure for statistical evaluation of pn junction leakage current based on CMOS image sensor technology

We propose a test structure to enable us to evaluate statistical distributions of small pn junction leakage currents of numerous samples in a very short time (0.1 - 10 fA, 28,672 n⁺/p diodes in 0.77s). This test structure is based on a CMOS active pixel image sensor, which contains a current-to-voltage conversion function by a capacitor and amplifiers of voltage signals in each pixel. The test structure can be designed easily because of a small number of mask layer requirements (at least one metal layer). Its simplicity has considerable benefits such as an easy fabrication for various processes without exceptional cares and also produces usefulness of statistical evaluation for anomalous pn junction leakage phenomena such as extremely large currents or dynamic and quantum fluctuations which show more and more as the device dimension shrinks.