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Politics : Formerly About Advanced Micro Devices -- Ignore unavailable to you. Want to Upgrade?

To: RDM who wrote (54172)	4/5/1999 4:43:00 AM
From: Process Boy	Read Replies (4) \| Respond to of 1573925

RDM - RE: <heard that the copper has less cross-talk between traces, but I have not heard a clear reason why.> Theory in a nutshell: Cu inherently has lower resistance and carries a higher current load per cubic unit, which reduces parasitic capacitance vs. Al. The longer a wire, the higher the resistance. However, the thicker the wire, the less resistance. Cu's lower specific resistance allows thinner wires with less parasitic capacitance (reduces cross-talk), and also allows higher speed (less RC delay). Choice of dielectric material (material between the wires) is also a fundamental factor in determining RC effects. Specific resistance values (rho) at 20deg C, (cmil)*(ohm/ft) Cu - 10.4 Al - 17.0 As for your question: <quantitatively how much faster are copper wires than aluminum wires for a typical .18 micron process?> This depends on the fundamental approach to improve overall speed of the circuit. Intel seems to contend at .18 that overall speed can be better enhanced by reducing gate delay in the transistors (stick with Al). AMD/MOT process evidently is endeavoring to improve overall processor speed by reducing RC delay (go to Cu), which allows for smaller pitches (tighter design rules) and reduces die size. Check out this post from Kash, and see if this sort of answers your question: Message 8688672 As for which process will ultimately be faster, we will have to wait until closer to the end of life of the process. Still speculative at this point. PB

To: RDM who wrote (54172)	4/5/1999 9:36:00 AM
From: Steve Porter	Respond to of 1573925

RDM, If you are looking quantitave answers I can't give them to you at the moment (don't have my reference handy, nor the time to adequately explain it). When I get a chance, if anyone is interested I will find and pull the relevant information. If you are curious about things like the difference in resistance beteween the two materials, you can always go to one of the basic electronics/physics/chem sites on the net. Hell you may well find all the equations to work out all of the questions ;-).... Sorry I don't have time to get into a detailed post, maybe this comming weekend I'll have the time. I'm not going to make the mistake that others make and give a quick little explanation of something that really needs to be understood to be of use. Regards Steve