In situ barrier formation using rapid thermal annealing of a tungsten nitride/polycrystalline silicon structure

Abstract

This letter describes the use of rapid thermal annealing (RTA) to form a barrier layer applicable to the gate electrode in dynamic random access memory devices with a stacked structure [tungsten nitride (WNx)/polycrystalline Si (poly-Si)]. After RTA, the reactively sputtered amorphous WNx film on the poly-Si was transformed to a low-resistive α-phase W and nitrogen-segregated layer. Most of the nitrogen in the WNx film was dissipated and a relatively small amount of the nitrogen was segregated at the interface of the α-phase W and poly-Si. The segregated layer was estimated to be 2 nm thick and revealed a silicon nitride (Si–N) bonding status. More importantly, we found that this thin segregated layer successfully protected the formation of tungsten silicide, even after RTA at 1000 °C for 2 min in a hydrogen environment.