Intrinsic characteristics of high-k devices and implications of fast transient charging effects (FTCE)

Fast transient charging effects (FTCE) are found to be the source of various undesirable characteristics of high-k devices, such as V_th instability, low DC mobility and poor reliability. The intrinsic characteristics of high-k transistors free from FTCE are demonstrated using ultra-short pulsed I-V measurements, and it is found that the intrinsic mobility of high-k devices can be much higher than what has been observed in DC based measurements. The FTCE model suggests that many of DC characterization methods developed for SiO₂ devices are not sufficiently adequate for high-k devices that exhibit significant transient charging. The existence of very strong concurrent transient charging during various reliability tests also degrades the validity of test results. Finally, the implication of FTCE on the high-k implementation strategy is discussed.