Characterization of ultralow-energy implants and towards the analysis of three-dimensional dopant distributions using three-dimensional atom-probe tomography

Abstract

The addition of a local electrode geometry has transformed the conventional atom probe into a high-speed, high sensitivity tool capable of mapping three-dimensional (3D) dopant atom distributions in nanoscale volumes of Si. Fields of view exceeding 100nm in diameter and collection rates exceeding 18×106at.∕h are possible with the local electrode geometry. The 3D evolution of dopants, specifically dopant clustering, grain-boundary segregation, shallow-doped B layers, Ni–Si layers, and preamorphization regions, was analyzed. A 200eV B11 implant in Ge-amorphized Si was mapped. The native surface oxide, 8-nm-deep B-doped layer, and Ge distribution were simultaneously mapped in 3D space. A subsequent Ni silicide process was analyzed to show Ni penetration through the doped layer. In a heavily doped poly-Si sample, a cluster of dimensions 2×7×8nm3 and containing 264 B atoms was identified at the intersection of three grains. This shows that annealing highly overdoped thin poly-Si layers does not facilitate uniformly doped and highly conductive gate contact layers for nanoscale complementary metal-oxide semiconductor transistors.