MOSFET's with one-mask sealed diffusion-junctions for ULSI applications

We describe a One-mask Sealed Diffusion-junction (OSDiff) structure for ULSI applications. Shallow junctions are formed at temperatures /spl les/900/spl deg/C using a WSi/sub 2/ diffusion layer and sealed with a TiN barrier-layer before metallization. The TiN-WSi/sub 2/ stack is patterned in a single lithography step with oxide hard-masks and spacers. A phenomenon of boron diffusion retardation in the presence of phosphorus is observed in the SIMS data, and is utilized to reduce one mask step in implanting the junction areas. Transistor data also shows improved deep submicron performance when the LDD regions are formed at the same diffusion step which forms the S/D junctions without the additional LDD implantations. Only ten masks are required for a full-CMOS process with two-level metallization, and the circuit density and speed are also improved.<
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