Formation of contacts to shallow junctions using titanium silicide with diffusion barriers

We investigated the process integration of shallow junctions' formation and titanium silicidation, Junctions were doped with boron or arsenic during diffusion in rapid thermal processing (RTP). Dopant sources were in the form of purl layers of B or As deposited on the silicon substrate by e-beam evaporation or molecular beam epitaxy (MBE), respectively. Contact formation to the junctions was preceded by Ti deposition, either on a sacrificial layer of amorphous silicon or directly on the dopant layer. We studied the role of dopant-metal compound formation as a diffusion barrier to prevent junction degradation during the silicidation process. Such a barrier completely stops silicide formation in the case of B but is less efficient for the As doping. It also impedes boron diffusion into the silicon substrate much more than arsenic diffusion. A standard process sequence, where the junction is formed first and silicidation follows, and a modified process flow, when silicidation is done in situ together with the junction doping lead to differences in the fabricated structures. Various analytical techniques such as secondary ion mass spectroscopy (SIMS), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), spreading resistance profiling (SRP), cross-section transmission electron microscopy (XTEM) and four-point probe were used for junction characterization. (C) 1999 Elsevier Science Ltd. All rights reserved.