A Focused Ion Beam Technique to Electrically Contact the Deep Trench Capacitor of a Single Active Memory Cell in the Sub 0.25µm Technology Regime

Abstract

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.