Imec & CMOS Partners Propose RMG Options For Further Transistor Scaling
Imec is testing and evaluating various options for
further transistor scaling using high-k dielectrics
and metal gates in a replacement metal gate (RMG) integration schemes.
Although RMG technology is inherently more complex
than gate-first integration, it has a number of advantages that allow
increasing the device performance and that widen the choices in terms of high-k and metal gate materials.
The R & D institute presented a number of noted papers on RMG at the 2012 VLSI Technology Symposium, which is taking place between June 12th and 15th, 2012, Honolulu, Hawaii, USA.
One of the current challenges to enable further device scaling is the choice of gate dielectric and gate electrode. For the selection of the gate electrode, the key parameters to consider are the work function, resistivity and compatibility with CMOS technology. Further scaling also requires continued improvement of the channel mobility, adding the options for improved stress management and also reliability control as a first-order consideration in the choice of materials and processes.
In the industry, the RMG approach is rapidly becoming
the integration scheme of choice, and an alternative for the gate-first
approach. In RMG, the high-k gate
dielectric is deposited in the beginning of the flow or just prior to gate
electrode deposition and the gate electrode is deposited after the formation of
the junctions.
A clear advantage is the enhancement of the channel
stress in shorter devices because of the dummy-gate removal, an intrinsic step
in RMG flow. RMG also allows metal gate processes with a lower thermal-budget,
which broadens the range of material options for work-function tuning and
reliability control. Additional advantages are a lower gate resistance compared
to gate-first, important for RF CMOS, and more room for mobility improvement.
With the eye on further scaling to sub-20nm technology
nodes, imec is now evaluating RMG technology for different applications.
Researchers are looking at different integration options, materials selection
and engineering, and compatibility with advanced modules and device
architectures, for which imec is collaborating with the major tool suppliers.
Regarding
its partners, imec says it is conducting fair comparisons of options, and
in-depth understanding of the physical mechanisms and techniques involved, and taking
the chance to explore the limits in performance and reliability.
