Investigation and Integration of Polycrystalline Silicon/TiN/SiON Gate Stack in Silicon on Thin Buried Oxide Complementary Metal Oxide Semiconductor Field Effect Transistors

Abstract

We developed fully depleted silicon on thin buried oxide (SOTB) complementary metal oxide semiconductor field effect transistors (CMOSFETs) with a polycrystalline-silicon (poly-Si)/TiN/SiON gate stack. We investigated the flat-band voltage (V fb) shift of the gate stack for the threshold voltage (V th) symmetry of SOTB CMOSFETs. We found that the V fb shift depended on both TiN thickness and thermal load. Thicker TiN above 15 nm is preferable for obtaining the midgap value of V fb with considering the thermal budget of the SOTB process. We also integrated the gate stack into SOTB CMOSFETs, which showed that the V th roll-off characteristics corresponded to the proper control of the effective work function by considering how the impurity-related work function modulation affects. Narrow channel characteristics of the TiN-gate SOTB CMOSFETs were also shown to be superior to fully silicided gate SOTB devices due to the less silicidation.