Impact of Tungsten Capping Layer on Yttrium Silicide for Low-Resistance n+-Source/Drain Contacts

In order to form a stable silicide having a low Schottky barrier height (SBH) for electrons, we employed a tungsten (W) capping layer on yttrium (Y) and investigated its physical and electrical properties. Our experimental results show that W can effectively protect against Y oxidation during silicidation. The Schottky barrier diode fabricated on p-type Si shows excellent properties, such as a near-ideal n-value of 1.02 and a very low reverse-biased current of 3.87 x 10(-7) A/cm(2), corresponding to a high SBH for holes of 0.767 eV. Also, the Schotky barrier diode fabricated on n-type Si shows a SBH for electrons of as low as 0.311 eV. We also confirm that the W capping layer can be applied to other rare-earth metals. The technology developed in this work is applied to silicide formation with no oxygen contamination to realize low-resistance source/drain contacts, which will improve the performance of metal-insulator-semiconductor field-effect transistors (MISFETs). (C) 2009 The Japan Society of Applied Physics