Selective Tungsten Metallization for 0.5 μm MOS Processes

Up to now conventional aluminum sputtering is a standard method for metallization in VLSI processes. With decreasing contact hole sizes down to the 0.5 μm range and aspect ratios ≫ 1, sputtering becomes more and more critical due to step coverage and reliability problems. A promising technique for future metallization processes is the contact hole filling by selective tungsten deposition. This metallization method was examined in a partially scaled 0.5 μm NMOS and PMOS process. Different contact schemes Si/TiSi2/W/Al, Si/W/Al and Si/Al were compared with regard to leakage current and contact resistance measurements, performed on diodes and Kelvin structures, respectively. Resistivity values 2 - 10^-7 - 5-10^-8 Ω cm² were evaluated for Si/TiSi2/W/Al contact systems. Contact hole structures, designed for scanning electron microscopy (SEM) analysis with dimensions down to 0.5 μbeen filled by selective W deposition.