Gregory Sullivan says:
There is a recent multi-part interview with Gordon Moore at the Scientific
American site. In part three of the interview he talks about the
technologies that might allow the continuation of Moore's Law for a while
longer, e.g., EUV extreme ultraviolet, bigger wafers. He also talks about
how it is easier to do multiple layers now which is relevant to partially
exploiting the third dimension.
The URL for part three of the interview is:
http://www.sciam.com/interview/moore/092297moore3.html
Excerpt:
SA: How about adding more layers to the chips?
GM: More layers are something we do now without much concern. Going from
one to two was tough, two to three was difficult, but five to six--piece
of cake. A technology has come in there that is really amazing. This is
the idea of chemical-mechanical polishing of the top surface. The problem
used to be that as you went through more layers, the polishing got all
screwed up. You'd get mountains and valleys and undercut levels, and
things didn't work well. Now between putting down every layer of
insulator and metal, we polish either the top of the metal or the top of
the insulator flat. So we're always working on a flat surface. And that
has really been a breakthrough technology in allowing multilayer
structures.
SA: How exactly do you polish them?
GM: We have a great big lapping machine with some goo on
there--chemical-mechanical, it's called. They use slurries that also react
somewhat chemically with the surface. It's not just grinding. But it gives
them a very flat surface. The end result is, we put five layers on top of
each other and then ask the design engineers, "Would you like another
layer of metal?"
SA: Do you think that trend will continue, that chips will get even
taller?
GM: I think it will, yes. I think that's one of the real levers we have to
work with.
End excerpt
Gregory Sullivan