By Nick Gilbert
For further transistor scaling, imec has tested and assessed different choices utilizing metal gates and high-k dielectrics in a replacement metal gate (RMG) integration scheme.
RMG technology is basically more intricate when compared to gate-first integration but it has several benefits, which include its role in improving device performance and providing more options in terms of metal gate and high-k materials. imec has presented several key papers demonstrating its development with RMG technology at the 2012 VLSI Technology Symposium, which is being conducted from June 12 to 25, 2012, in Honolulu, USA.
Selecting gate electrode and gate dielectric is one of the current issues for enabling further device scaling. Compatibility with CMOS technology, resistivity, and work function are the important factors to be considered in the choice of the gate electrode. Further device scaling also entails constant channel mobility improvement, increasing the choices for enhanced stress management, and also reliability control as a major concern in the selection of processes and materials.
In RMG technology, the high-k gate dielectric deposition is done during the start of the flow or just before the deposition of the gate electrode. The gate electrode deposition is done after the creation of junctions. RMG flow eliminates dummy gate, thus improving channel stress in smaller devices. RMG enables metal gate processes with a minimal thermal budget, which increases the material choices for reliability control and work-function tuning. It provides a lower gate resistance than gate-first, an essential requirement for RF CMOS, and allows mobility improvement.
imec, which aims at further scaling to sub-20 nm technology nodes, is now assessing RMG technology for various applications, exploring different materials choice and engineering, integration options and compatibility with sophisticated device architectures and modules.
imec conducted the research together with major partners in its key CMOS programs, including Sony, Fujitsu, SK hynix, Elpida, TSMC, Samsung, Panasonic, Micron, Intel and Globalfoundries.