Leakage Reduction by Thermal Annealing of NiPtSi Silicided Junctions and Anomalous Grain-Incompatible Pt Network

Abstract

Using highly reliable damage-free junctions, the effectiveness and limitation of Pt addition for the stabilization of thin NiSi films are accurately specified and practically formulated in terms of the thermally induced leakage. In addition to the thermal leakage, the unexpected emergence of initial leakage is also witnessed and attributed to the emission of Si interstitials during silicidation and the subsequent formation of boron interstitial clusters. Rapid evanescence of the initial leakage by post-annealing is also successfully demonstrated owing to the Pt-induced thermal stabilization. Moreover, unlike other Pt distributions considered so far, Pt atoms are revealed to concentrate in a distinctive manner, forming an anomalous in-layer web-like structure which even extends within single NiSi grains. This grain-incompatible Pt network is thought to be a remnant of Pt-aggregation around grain boundaries of an earlier metal-rich silicide phase (e.g., Ni2Si), incorporated and left intact in the final phase (i.e., NiSi). Such intermediate-phase Pt-rearrangement may have interfered with the phase transition sequence and reoriented the final NiSi grains to constitute a crystallographically stable and thermally robust interface structure, resulting in the effective stabilization by Pt addition.