Please note that JavaScript and style sheet are used in this website,
Due to unadaptability of the style sheet with the browser used in your computer, pages may not look as original.
Even in such a case, however, the contents can be used safely.
High-k Transistor
Reducing Gate Current Leakage
NEC Electronics employs High-k over silicon dioxide as the gate insulator from 55 nm products onwards, obtaining an 80% reduction in standby power consumption. Figure 1 shows how the performance of the NEC Electronics High-k transistor compares to that of conventional High-k transistors and SiON (Silicon Oxynitridation) transistors.
Thin High-k Layer to Support Wider Range of Applications
To boost performance by reducing transistor sizes, gate insulators must be made thinner. But when conventional SiON gate insulators are made thinner, correspondingly more gate leakage occurs. This is why High-k dielectrics were proposed. Physically speaking, the use of a material with higher conductivity will produce the same result as thinning the insulator layer.
However, simply replacing SiON with a High-k dielectric will only increase the threshold voltage and thus limit the transistor's scope of application.
High-k Transistor Limits GIDL and Enhances Performance
To decrease off-leakage current in conventional SiON transistors, it is necessary to increase the threshold voltage (VTH) by increasing the concentration of impurities in the channel. But these impurities work to disperse electron and hole carriers, which hinders electron mobility and decreases the on-current.
High-k dielectrics increase the threshold voltage without requiring higher impurity concentrations in the transistor channel. Lower impurity concentrations greatly reduce gate-induced drain leakage (GIDL) compared to conventional transistors with SiON dielectrics. They also enhance the performance of the transistor by increasing carrier mobility and the on-current.
Combined with optimized channel design, the introduction of High-k gate technology from NEC Electronics enabled an across-the-board reduction in every source of leakage by MOS transistors. At the same time, it enabled higher performance. NEC Electronics was the first in the industry to introduce High-k gate insulators in transistors for commercial use.
|
|