Series resistance of self-aligned silicided source/drain structure

The external resistance of the self-aligned silicided source/drain structure is examined by two-dimensional simulation considering recession of the contact interface due to the consumption of silicon during the silicidation process. It is observed that the recessed contact interface forces a significant amount of current to flow into the high-resistivity part of the junction, resulting in an increase of resistance as large as several hundred ohms-micrometers in comparison with the surface contact structure. The increase scales up with the scaledown of the minimum feature size, and the expected benefits of the salicide structure diminish for the sub-half-micrometer devices. A simple analytical explanation is proposed. By considering the recession of the contact interface, the reported high external resistance of short-channel MOSFETs is explained. Different source/drain contact types are compared, and it is concluded that the conventional salicide process should be modified for sub-half-micrometer devices