AMD Working Quietly On Copper
Interconnects
(05/22/98; 4:00 p.m. EST)
By Alexander Wolfe, EE Times
Though overshadowed by IBM's high-profile effort to field copper
interconnects, Advanced Micro Devices is quietly forging ahead
with development work to take the next-generation semiconductor
technology from the research lab into the real world, EE Times has
learned.
To date, Sunnyvale, Calif.-based AMD (company profile) has
successfully fabricated two test chips with copper interconnects, a
company official said. "One is what I'll call a pure test [chip]," said
Don Wollesen, director of technology and reliability engineering at
AMD. "It has structures on it, such as transistors, wires and
contacts -- all the nuts and bolts you use to make an integrated
circuit. We made some of those and things looked pretty good."
AMD's second test effort involved far-more-complex static
RAMs. "We don't sell these, but we used them as kind of an
interim test vehicle," said Wollesen. "We've got two of them, a
256-K SRAM and a 1-megabit SRAM."
Wollesen said the SRAMs were fabricated with copper on the
upper layers in 1997.
As for the current status of copper at AMD, Wollesen said he was
not free to provide specifics. "We're continuing to try to find out
where the limit on the minimum feature size is and what our
capabilities are."
In working with copper, Wollesen found implementing the
interconnects on the upper layers of an IC, where loose-pitch
structures typically appear, is relatively straightforward. "You
don't have an aspect-ratio problem, which you run into if you're
trying to do, for example, a 0.2-micron-wide [copper] line in a
0.18-micron technology," he said.
Stumbling Block
Indeed, depositing copper interconnects on the lower metal layers
of an IC, where such high-aspect-ratio vias and holes appear, is a
major stumbling block for today's technology. The problem is that it
is difficult for current-generation copper deposition and plating
equipment to completely fill in those deep, wide gaps. Often, voids
or cracks remain in the copper. |
