Soft Defect Localization Technique for Design and Debug on DRAM Devices

A functional fail of a DRAM is analyzed by using an analog output of the device as an input signal of a microscope. Local heating by an IR laser changes the pass/fail behavior and thus the analog output of the DRAM. Although the observed spots do not belong to the physical defect, they give a starting point for further electrical analysis leading to the root cause of the failure. The paper will present a case study on a state-of-the art DRAM device failing with a timing problem. Especially the test aspects as well as the setup for the temperature dependent localization will be described. Finally an interpretation of the results will be proposed.