Abstract :
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With the advances in technology, the integrated circuit (IC) chip size, complexity, and device packing density is continuously increasing, which causes reduction in the minimum feature size used in IC’s. As a first-order approximation, therefore, this should proportionally increase the circuit speed. Indeed, for smaller circuits it does happen. However, for larger circuits, the net effect of this “scaling of interconnections” is reflected into an appreciable RC time delay especially for VLSI. Analytical expressions have been developed to relate this time delay to various elements of technology, i.e., interconnection material, minimum feature size, chip area, length of the interconnect, etc. Calculations of time delay for interconnections made of poly Si, WSi2, W, and Al have been done and they indicate that as the chip area is increased and other device related dimensions are decreased the interconnection time delay becomes significant compared to the device time delay and dominates the chip performance. Changing the design rules, multi-layer interconnections, insertion of repeaters and optical fiber interconnections can reduce RC time delay in VLSI circuits significantly.
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