A transmission line model for silicided diffusions - Impact on the performance of VLSI circuits

A theoretical development of a transmission line model for a totally silicided diffusion is presented. Both the silicide and the diffusion sheet resistivities and the specific contact resisitivity are incorporated; this is in contrast to earlier models for contact holes only in which the silicide sheet resistivity equals zero. The model is applied to typical MOS structures, including single-section and three-section structures, in order to calculate the contact resistance contribution to total resistance. The results are used in conjunction with device equations addressing the device and circuit performance of small-geometry MOSFET's. They show that, for n-channel devices with a gate length of 1 micron, a factor-of-two increase in circuit performance can be expected with silicides. For p-channel devices, however, the expected performance gain as a result of silicides is a factor of 10.