Interactions Between Metallization or Diffusion Layers and Doped Silicon Plugs in Deep-Submicron Contact-Holes

Abstract

ABSTRACTPhosphorus-doped polycrystalline silicon used to plug the high-aspect-ratio, deep-submicron contact-holes connecting suicide metallization layers and substrate diffusion or silicide/polycide layers used in prototype 64 and 256 mega-bit DRAM devices acts as a dopant source at the silicidc/plug and plug/substrate interfaces during thermal processing. This outdiffusion of phosphorus from the contact-hole plug can lead to increased contact resistance which degrades device reliability and performance. Non-doped silicon, titanium, and titanium nitride films have been investigated as phosphorus outdiffusion buffer or barrier layers which reduce or prevent interaction between the doped contact-hole plug and surrounding conduction layers. Non-doped silicon diffusion buffer layers alternately deposited with in situ-doped silicon dopant source layers have been found to be effective in reducing outdiffusion into the substrate whereas a TiN diffusion barrier layer sputter deposited between the plug and WSix metallization prevents dopant outdiffusion into the WSix layer.