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

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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_{\text{fb}}) shift of the gate stack for the threshold voltage (V_{\text{th}}) symmetry of SOTB CMOSFETs. We found that the V_{\text{fb}} shift depended on both TiN thickness and thermal load. Thicker TiN above 15 nm is preferable for obtaining the midgap value of V_{\text{fb}} with considering the thermal budget of the SOTB process. We also integrated the gate stack into SOTB CMOSFETs, which showed that the V_{\text{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.
2012-07-25