  Soaring demands of multi-stacked memory devices request urgent development of
backside contact electrode technologies, such as high aspect ratio etching,
metallization, and inspection methods. Especially the complex metal contact
process should be monitored for each manufacturing step to filter the defective
samples and to maintain the high yield of production. Among the inspection
methods for detecting the electrical connections, there is voltage contrast
(VC)-SEM and conducting AFM (C-AFM). In this report, we investigated the two
inspection methods for testing designed samples with different contact hole
states. The VC-SEM data shows the contrast variation at the contact holes, from
which one may discern the contact status with an optimum voltage. The C-AFM
results clearly demonstrate a finite electrical current in the connected
contact, while a negligible current in the disconnected one. Finally, we
discuss insights of using the two methods for analyzing the contact hole
technologies with high aspect ratios.
