You guys gotta love this, that famous notch!
techweb.com
Intel Process Tweak Improves
Pentium III
(12/09/99, 6:37 p.m. ET)
By Peter Clarke, EE Times
WASHINGTON - Intel is manufacturing
Pentium IIImicroprocessors with better than
800-MHz clock frequencies byusing a
refinement of CMOS process technology
described by researchers at this week's
International Electron Devices
Meeting(IEDM).
The "notched-poly" process refinement described by
Tahir Ghani, senior engineer with Intel's logic
technology development group in Portland, Ore., has
already been included in Intel's 0.18-micron CMOS
process and in circuits manufactured with transistor gate
lengths of 0.1 micron (100 nanometers).
At a session after his presentation, Ghani said Intel had
"made Pentium III devices but not shipped [them] yet."
He later qualified that statement, saying, "Some devices
have shipped, but we haven't announced that yet."
Regardless, "The clock frequency is better than 800
MHz," Ghani said.
The development strayed from the norm at IEDM,
where technology described in presentations normally
shows up in circuit implementations at the International
Solid-State Circuits Conference (ISSCC) the following
year, or sometimes two or more years later.
Intel's 0.18-micron process technology normally
produces transistors with a 0.13-micron gate length, but
in his presentation Ghani said a method had been
devised that allowed a notch to be introduced at the
bottom of each transistor's polysilicon gate, thereby
narrowing the gate length to 100 nm.
Another advantage of the notched-poly process is that
it allows the continued use of 248-nm lithography,
Ghani said.
The shorter gate length, together with other refinements
described in the paper, reduces the gate capacitance
and allows circuits to be built with higher-speed
performance at a reduced operating voltage (1.2 to 1.5
V) and with higher current drive and low leakage
current.
"The drive current is increased by about 10 percent,"
said Ghani.
He would not offer specifics on Intel's method for
making the gate-shortening notches, but he did say that
it's "cost-free" (implying that it requires no extra process
steps) and that the lateral and vertical dimensions of the
notch are highly controllable -- an important factor in
repeatability and reliability.
Ghani added that Intel uses a 16-Mbit SRAM design as
a test vehicle for its 0.18-micron process node, and that
such an SRAM, operating at a 1.16-GHz clock
frequency, has been built using the notched-poly
process. More details on that circuit are due to be
revealed in February.
Other features of the notched-poly refinement are an
optimization of the source and drain doping implantation
and annealing, and a change from a titanium to a cobalt
salicidation process; but Ghani stressed that no change
was required to Intel's standard gate oxide or its 2-nm
thickness.
Noting that reliability of the gate oxide is a major
concern with leading-edge processes, Ghani said tests
indicated the new configuration would exhibit a lifetime
in excess of 10 years at 1.5-V operation.
"The variations are similar to what we see for straight
poly," he said. "The oxide is extremely robust." |
