Advance static random access memory soft fail analysis using nanoprobing and junction delineation transmission electron microscopy

Abstract

Nanoprobing was used to analyze the soft cell failure of submicron static random access memory (SRAM) at cell level by means of a Zyvex S100 nanomanipulator system inside a scanning electron microscopy and a multiprobe atomic force probe system, respectively. For the 256Kbyte dual-port SRAM block, the failure areas exhibit very weak positive-channel field effect transistor drain currents of several magnitudes below the target values, while the drain currents of negative-channel field effect transistor cell transistors are in the expected range. A junction delineation or junction stain was applied to transmission electron microscopy samples to delineate areas with different doping levels so as to make the fail sites visible. Due to the difference in etching behavior of the fail and a reference area, missing lightly doped drain extensions and a partially blocked source/drain implantation were identified as the failure mechanisms.