Refractory Metals and Silicides for Very Large Scale Integration Applications,
STANFORD UNIV CA CENTER FOR INTEGRATED SYSTEMS
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Continuous advancements in technology have resulted in integrated circuits with smaller device dimensions, and larger area and complexity. The overall circuit performance has depended primarily on the device properties. However, the parasitic resistance and capacitance associated with interconnections and contacts, as for an MOS transistor, are now beginning to influence the circuit performance and will be the primary factors in the evolution of submicron VLSI technology. Examples of contact resistance shallow junction series resistance and rc time delay of interconnections, respectively are shown. Results of theoretical modeling indicate that below 1 micron minimum feature size the impact of these parsitics will seriously hurt the circuit and system performance. The RC time delay, the IR voltage drop, the power consumption and the crosstalk noise due to these parastics will become appreciable. Thus even with very fast devices, the overall performance of a large circuit could be seriously affected by the limitations of interconnections and contacts. It is evident that refractory metals and silicides are playing increasingly important roles. It must be also be pointed out that these materials will not replace aluminum but compliment it. The materials which have been used or proposed for forming interconnections can be broadly classified into four categories heavily doped polysilicon, low temperature metals, high temperature refractory metals and metal silicides. Table compares properties of some of these materials showing their compatibility with present silicon fabrication technology.
- Electrical and Electronic Equipment
- Metallurgy and Metallography