"I am assuming that if you need to turn more than one transistors on in a close proximity(sp), why not hook them up together at the floor level rather than go up on top and come down again with aluminum wires. What do you think?"
Allen, you usually would as this would minimize space. However, there are various reasons why this may not be done. For one, even though a transistor is is close proximity to another, they may not be exactly the same device. Let's say you want to a Tx with a low Vt as in the case of a pass transistor. You may want to minimize the body effect caused by altering your Vsb. In this case, that Tx would have to sit in it's own well (perhaps a triple well device) so that you may tie the body to ground or Vcc for an nmos or pmos repectively. In this case, you may not be able to simply route the diffusions together on your layout. Another reason may be that a guard ring for lowering your Rs and Rw, to prevent your CMOS from latchup, blocks a direct routing of your diffusions. There are a large variety of devices that are developed for specific applications; transistors vary widely. This is why AMD, Intel, etc. have a technology team (AMD's is much more innovative and efficient than Intel's). I hope this answers your question (I may have misinterpreted it).
In regards to the learning curve discussion, I would like to comment that AMD has been able to master this curve much more adeptly than Intel. The media gives AMD crap about having a processor that is "one year behind blah, blah, blah). How long has Intel been working on x86 microprocessors? 25 years? What about AMD? I thought so. However, AMD has been able to develop design methodology, design implementation, process technology, etc. which resulted in the K6 (far superior to PPro in my humble opinion) in a fraction of Intel's time. To be frank, AMD had to start from square one. This fact is rarely stated in the media. As in automobiles, a late starter will understandably stumble as they struggle with a daunting curve. However, the second try is usually far superior; think of the Japanese and the first Toyota which competed with the Mustang or the Koreans today. |
