Decoupling the Fermi-level pinning effect and intrinsic limitations on p-type effective work function metal electrodes

A review of literature combined with recent experimental results addressing the intrinsic and extrinsic factors controlling the effective work function (EWF) of metal gate electrodes on Hf-based high-K dielectrics is discussed. Through a systematic study including accurate extraction of EWF, our observations suggest, unlike popularly perceived, intrinsic E"f-pinning does not limit the EWF tuning on high-K. Also, a critical issue challenging the maintenance of high EWF metals at low effective oxide thicknesses (EOT), due to a new phenomena described as the ''V"f"b roll-off'', is reported for the first time.