Electron holography analysis of a shallow junction for planar-bulk metal-oxide-semiconductor field-effect transistors approaching the scaling limit

Abstract

We investigated electrostatic potential distributions in source∕drain extensions (SDEs) in metal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated using state-of-the-art junction formation technology. We first demonstrate that electron holography can directly reveal potential distribution in scaled MOSFETs when specimen preparation artifacts are reduced, which we did by using back side low-energy Ar ion milling. Second, we examine the potential distributions in SDEs in a scaled (30-nm-gate-length) MOSFET fabricated by using a combination of cluster B implantation, millisecond annealing, and multihalo implantation. The results show that these junction formation technologies enable fabrication of very abrupt and shallow (10-nm-deep) SDE junctions. In addition, our experimental analysis, in conjunction with a Monte Carlo doping-process simulation, indicates that B channeling along the ⟨110⟩ direction of the Si substrate during the implantation process significantly blurs the SD junction profiles and that multihalo implantation can increase junction abruptness. Third, we show that our experimental results describe well the roll-off characteristics of the MOSFETs.