flower@hpcc01.HP.COM (Graham Flower) (02/20/91)
Please excuse my ignorance but I'm not sure I understand why supercondu-
ctor interconnects are such an advantage that they justify the costs.
A couple of possibilities occur to me:
1. Reduced interconnect resistivity reduces IR drops on supply
busses and so reduces chip area devoted to Busses.
2. Reduced interconnect resistivity decreases ground noise.
3. Reduced interconnect resistivity increases signal propagation
speed considering the interconnect as a stripline transmission
line.
Could somebody please educate me on which of these is most important or
add the proper considerations to this list? Thanks.
______________________________________________________________________________
Graham Flower ms 90-TT | Better to have convictions and act on
Hewlett-Packard 350 W Trimble Rd | them, even if they are wrong, than to
Microwave Semiconductor Division | waffle in indecision endlessly.
San Jose, California, 95131 |rosentha@loki.Stanford.edu (Peter A. Rosenthal) (02/21/91)
Superconducting interconnects allow some performance advantages in certain applications. For short on chip wiring, they are not particularly useful. Aluminum can carry ample current, and the power dissipated by the wiring is small compared to the active device dissipation. The device resistances and contact resistance dominate over the wiring resistance too, so the rc time constants are not limited by the wiring. For connections greater than about 2 cm, the wiring resistance of high quality aluminum does indeed limit the performance both in terms of speed and dissipation of power. For very large IC's and chip to chip interconnects one would get a performance improvement by going to superconducting interconnects, but the problems of packaging ie. thermal expansion mismatch and heatsinking become major headaches. High temperature superconductors will probably be wedded to semiconducting IC's in the not to distant future but substantial basic research and development must be done first. Peter Rosenthal