Posted on October 4, 2017
GlobalFoundries and IBM Research at Albany NanoTech have recently published their work with QuantumATK providing atomistic-level insight into the interface between semiconducting Ge and metallic TiGe used in contacts for sub-10nm nodes. The study gives directions on how to minimize the contact resistance at the interface.
1.The work  shows that the Schottky barrier heights (SBHs) of the TiGe/Ge contact depend strongly on the phase of TiGe and on the different crystallographic orientations of Ge. This indicates that SBHs are extremely sensitive to the atomic structure of the interface, which is challenging to characterize even with sophisticated experimental measurements. Atomic-scale modelling tools are therefore of paramount importance in this case. The atomic-scale modelling tools in ATK are designed to study metal-semiconductor interfaces, because they describe the interface using the physically correct boundary conditions, and account correctly for the semiconductor band gap and doping.
2. This work also shows that by increasing the doping density in the semiconductor, it is possible to reduce the contact resistance and convert the Schottky barrier into Ohmic, which is crucial for sub-10 nm nodes.
Good agreement with experiments
A number of calculated properties such as the value of Ge band gap, the SBHs, as well as the trends of the current-voltage (I-V) curves and of the contact resistance with doping are in a good agreement with the experimentally determined values as, for example, shown in Panel 4 of the Figure below.