Considerably suppressed gate-induced drain leakage (GIDL) shifts of N2O-based n-MOS-FET's after hot-carrier stress with different gate voltages are observed. The mechanisms involved are studied by dividing gate-oxide traps into sub-interface and bulk-oxide traps, and by means of computer simulations on electric-field distribution and carrier filling of these traps. It is demonstrated that sub-interface and bulk-oxide hole detrapping during stressing are mainly responsible for the respective GIDL shifts under two diff erent stress conditions of VG=0.5VD and VG=VD, with the effect of the former larger than the latter. In view of this, it is proposed that MOSFET's with N2O-nitrided or es-pecially N2O-annealed NH3-nitrided gate oxide have not only fewer pre-existing sub-interface and bulk-oxide hole traps, but also greatly suppressed generation of hole and neutral electron traps due to the formation of a nitrogen-rich layer near the SiO2/Si interface through N2O treatment.

Oxynitrides prepared by double nitridation in nitric oxide (NO) and nitrous oxide (N2O) are compared to the one with a single NO nitridation. Based on various hot-carrier stresses, harder oxide/Si interface, less charge trapping and generation of electron/hole traps in oxide, and larger chargeto-breakdown are observed for the doubly-nitrided gate dielectrics than the singly-nitrided one. By analyzing the nitrogen profiles in these oxynitrides, it is revealed that the involved mechanisms lie in the smaller distance of peak nitrogen concentration from the oxide/Si interface and the higher nitrogen content near the oxide=Si interface in the doublynitrided oxynitrides.

The energy levels of interface states generated in n-MOSFETs during hot-carrier stressings under maximum substrate-current condition (VG～VD/2) are studied by measuring their GIDL current, which is believed to result from trap-assisted tunneling. It is found that di€erent VG results in interface-state distribution with different energy-level edges in the forbidden gap. This phenomenon gives a new insight on the mechanism of interface-state generation: the energy release when holes are neutralized by electrons during stressing, depends on the energy the carriers obtain from the stress field which is related to VG and VD. Smaller released energy prefers to break those bonds with lower binding energy (e.g. strained Si-O bonds) and thus creates shallow interface states and vice versa. Hence, the effects of these shallow interface states on device reliabilities are a major concern because they would be highly created by the low operating voltage of MOSFETs. In addition, it is suggested that interface traps which are most effective in assisted tunneling are those closest to the mid-gap from the analyses on the barrier height of tunneling.

Performances of gate dielectrics prepared by double-nitridation in NO and N2O are investigated. Stronger oxide/Si interface bonding, less charge trapping and larger charge-to-breakdown are observed for such gate dielectrics than singly NO-nitrided gate dielectric. The physical mechanisms behind the findings are attributed to larger nitrogen peak concentration located almost at the oxide/Si interface and total nitrogen content near the oxide/Si interface of these gate dielectrics.

Oxynitrides were grown on n-and p-type 6H-SiC wet N2O oxidation (bubbling N2O gas through deionized water at 95 C) or dry N2O oxidation followed by wet N2O oxidation. Their oxide/SiC interfaces were investigated for fresh and stressed devices. It was found that both processes improve p-SiC/oxide deteriorate n-SiC/oxide interface properties when compared to dry N2O oxidation alone. The involved mechanism could be enhanced removal of unwanted carbon compounds near the interface due to the wet ambient, and hence a reduction of donor-like interface states for the p-type devices. As for the n-type devices, incorporation of hydrogen-related species near the interface under wet ambient increases acceptor-like interface states. In summary, the wet N2O oxidation can be used for providing comparable reliability for n-and p-SiC MOS devices, and especially obtaining high-quality oxide-SiC interface in p-type MOS devices.

1/f noise, AC hot-carrier stress, dynamic stress, MOSFET's, nitridation.

Response mechanisms of hydrogen sensor based on a metal-insulator-SiC (MISiC) Schottky-barrier diode are analyzed. A physical model is established for the hydrogen sensor by combining thermionic emission with quantummechanical tunneling of charge carriers, and considering hydrogen-induced barrier-height modulation. Simulated results are in good agreement with experimental data. Relation between device performance and insulator thickness is investigated using the proposed model, and the optimal range of insulator thickness can be determined by taking into account the tradeoff between device sensitivity, reliability and resolution for high-temperature applications.

The interface and bulk qualities of N2O-based oxides are investigated by means of backsur-face Ar+ bombardment and hot-carrier stressings. It is deduced that there exists a large mechanical stress near the oxide/Si interface for N2O-grown oxide which might result from its initial accelerated growth phase, while the residual stress is negligible for N2O-nitrided oxide. Therefore, in view of another stress induced by the bombardment, the interfacial properties can be improved for N2O-grown oxide through stress compensation, but deteriorate for N2O-nitrided oxide due to increased mechanical stress, indicating fresh N2O-nitrided oxide itself has excellent interfacial and bulk qualities for high-per-formance devices. Moreover, for N2O-grown oxide, the improvement exhibits a turnaround behavior for long bombardment times due to stress over-compensation

Degradation mechanisms contributing to increased 1/f noise of n-channel metaloxide-semiconductor field-effect transistors (n-MOSFETs) after different hot-carrier stresses are investigated. It is demonstrated that for any hot-carrier stress, the stress-induced enhancement of 1/f noise is mainly attributed to increased carrier-number fluctuation arising from created oxide traps, while enhanced surface-mobility fluctuation associated with electron trapping at preexisting and generated fast interface states and near-interface oxide traps is also responsible under maximum substrate-and gate-current stresses. Besides thermal-oxide n-MOSFETs, nitrided-oxide devices are also used to further support the above analysis

1/f Noise behaviors of nitric oxide (NO)-nitrided n-MOSFETs are investigated. Greatly decreased 1/f noise at low frequencies and enhanced stability of noise properties under hot-carrier stress are achieved by annealing NO-nitrided gate oxide in an N2O ambient. The physical mechanisms involved lie in the fact that N2O annealing partly removes the oxide traps situated farther away from the oxide/Si interface and simultaneously increases interfacial nitrogen incor-poration.