A new diagnostic test for operating margin problems in LSI memory

A new diagnostic test technique for operating margin problems in LSI memory has been developed that makes it possible to distinguish the failed circuit block exactly even if plural failed blocks exist. This method consists of two techniques using a newly developed time domain method (TDM). One is a technique that divides the multiple failure due to the plural failed circuit blocks into single failures. The other is a technique that distinguishes the single failure mode and then locates the failed circuit block. Moreover, a detailed diagnostic technique, combining bit mapping with the new diagnostic test technique, has also been developed. This technique enables distinguishing the failure mode more precisely. It is shown that 50 percent of the distinguished failure modes have 1-block resolution and 33 percent of them have 2-block resolution. For practical purposes, the failed circuit block can almost be distinguished with 1-block resolution by investigating the failure modes in connection with the physical layout.