It is generally conceived that the introduction of high-k gate dielectrics is inevitable for the technology nodes of 50 nm and beyond, in order to satisfy the stand-by power requirement without sacrificing metal oxide semiconductor field effect transistor (MOSFET) performance.
HfO2 is considered as one of the most promising high-k dielectrics. However, threshold voltage instability and inadequate mobility of HfO2 MOSFETs are major issues that remain to be solved.
For the threshold voltage instability issue, we found that the exponential value of △Vth for pMOSFETs with HfO2 gate dielectric is voltage and temperature dependent due to charge trapping in bulk HfO2. More efforts on the model of time evolution of Vth instability, so that we could extrapolate ten years lifetime for devices by this model, are necessary.
Introduction of the strained silicon could enhance channel mobility while locally strained pMOSFETs with HfO2 gate dielectric have not yet been reported. More research efforts are needed to understand channel mobility and reliability of this structure, and their impacts on future ULSI technology.
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ITRS 2004
Year of Production
2004 2005 2006 2007 2008
EOT (physical) for
high-performance (nm) 1.2 1.1 1.0 0.9 0.8
Electrical thickness adjustment for gate depletion and inversion layer effects (nm)
0.8 0.7 0.7 0.4 0.4
Nominal gate leakage current
density limit (at 25°C) (A/cm2) 450 520 600 930 1100
Manufacturable solutions are known Manufacturable solutions are NOT known
Table 1-1 2004 International Technology Roadmap for Semiconductors.
The color shade means the solution known and unknown for physical limit.
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