Integration of ALD AlN work function tuning layers

We investigate the impact of AlN buffer layers on metal gate work function (WF) of TiN metal inserted polysilicon stacks on silicon dioxide (SiO₂) and high-k gadolinium silicate (GdSiO). Atomic layer deposition (ALD) technique is used to achieve atomic control of the buffer layer thickness. High WF of 5.2 eV suitable for p-MOSFETs are obtained by ALD AlN buffer layers and the principles of dipole based WF tuning can be transferred to GdSiO based high-k stacks. The applicability of the AlN buffer layer technique is demonstrated by integration into p-MOSFETs. Hole mobility is found to be unchanged for devices with AlN compared to reference devices without buffer layer.