27 October 2007

Limitations of the existing interconnect technologies

Performances of deep sub micron ICs are limited by increasing interconnect loading affect. Long global clock networks account for the larger part of the power consumption in chips. Traditional CAD design methodologies are largely affected by the interconnect scaling. Capacitance and resistance of interconnects have increased due to the smaller wire cross sections, smaller wire pitch and longer length. This has resulted in increased RC delay. As technology is advancing scaling of interconnect is also increasing. In such scenario increased RC delay is becoming major bottleneck in improving performance of advanced ICs.




Figure (1) Gate and interconnect delays Vs technology nodes [1]

This problem is illustrated in Figure (1).

Here the gate delay and the interconnect delay are shown as functions of various technology nodes ranging from 180nm to 60nm. The interconnect delays shown assumes a line where repeaters are connected optimally and includes the delay due to the repeaters. From the graph it can be observed that with the shrinking of technology gate delay reduces but interconnect delay increases.

Reference

[1] Kaustav Banerjee, Shukri J. Souri, Pawan Kapur, And Krishna C. Saraswat, 3-D ICs: A Novel Chip Design for Improving Deep-Submicrometer Interconnect Performance and Systems-on-Chip Integration, Proceedings Of The IEEE, pp.602-633,Vol. 89, NO. 5, May 2001, 0018–9219/01, 2001, IEEE

[2] Kaustav Banerjee, Shukri J. Souri, Pawan Kapur and Krishna C. Saraswat, 3-D Heterogeneous ICs: A Technology for the Next Decade and Beyond, 5th IEEE Workshop On Signal Propagation On Interconnects, Venice, Italy May, 13-16, 2001

[3] Jason Cong, An Interconnect-Centric Design Flow for Nanometer Technologies, Proceedings of the IEEE, pp.505-528, VOL. 89, No. 4, April 2001, 0018–9219/01,2001 IEEE

[4] Sungjun Im, Navin Srivastava, Kaustav Banerjee, and Kenneth E. Goodson, Thermal Scaling Analysis of Multilevel Cu/Low-k Interconnect Structures in Deep Nanometer Scale Technologies, Proceedings of the 22nd International VLSI Multilevel Interconnect Conference (VMIC), Oct. 3 - 6, Fremont, CA, pp. 525-530, 2005.

[5] Demystifying 3D ICs: The pros and cons of going vertical, http://www.ece.ncsu.edu/muse/papers/dtoc2005.pdf, 9/5/2007

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