High density test structure array for accurate detection and localization of soft fails

To resolve performance yield issues it is required to detect and localize soft fails such as a contact having 500 ohms instead of its nominal 50 ohms. Soft fails can only be detected within very small test structures, which requires an array design to efficiently use the area of test chips. Here we present a novel high density test structure array, which will enable accurate 4 terminal measurements of 1000 or more very small devices under test (DUT) within each array. On average, only 2 selection devices are required per DUT, which will provide outstanding utilization of the test chip area. Experimental results reveal that within this array traditional test structures can be used beyond their intended purpose to detect additional defect types, which opens the door to significant reduction of overall mask and wafer consumption.