Abstract
Focused ion beam (FIB) techniques are continuously improved to meet the demands of shrinking device dimensions and new technologies. We developed a simultaneous milling and deposition FIB technique to provide electrical contact to small buried targets in semiconductors. This method is applied to directly connect the deep trench (DT) capacitor of a DRAM single cell in deep submicron technology. By carefully adjusting the deposition parameters (scanned area < (0.3 µm)2, beam current < 20 pA) we are able to influence diameter, depth and Pt fill properties of the hole to meet the very restricted requirements for successful DT connection (hole diameter < 200 nm at DT level). Electrical measurements are performed on DRAM single cells after connecting buried plate (n-band), p-well, wordline, bitline and DT. The probe pads were Pt, deposited with ion beam assistance, on top of highly insulating SiOx, deposited with electron beam assistance by using a dualbeam FIB. The read and write conditions of an active memory cell are studied. The presented method increases the capabilities to localize and characterize trench related failure mechanisms.
