Abstract
In DRAM devices, many failures only appeared in a specific operating state on chips during functional tests. Dynamic photon emission microscopy (D-PEM) is a useful technique in failure analysis for emitted photons when the device under test (DUT) is electrically exercised. Therefore, D-PEM analysis combined with specific external triggers in functional test can activate the chip, and thereby expand the range of detectable defects and increase the chances of finding a specific failure mode. In this study, we will discuss various cases of external triggers applied from the tester. This method can be used to detect emission which did not show up in conventional test condition in PEM method for localizing active fails in DRAM. Then, after localizing the site of failure, more detailed physical visualization by Focused Ion Beam (FIB) cross section image, Transmission Electron Microscope (TEM), and Energy Dispersive X-ray microscopy (EDX) revealed main causes of failure. We believe that our method could be a future solution for increasingly difficult and diverse failures modes in the DRAM industry.
