Electrical properties of different NO-annealed oxynitrides

This journal issues contain proceedings of the 2nd International Conference on Amorphous and Crystalline Insulating Thin Films II ... 1998Performances 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.postprin

Improved interface properties of p-type 6H–SiC/SiO2 system by NH3 pretreatment

Effects of preoxidation NH3 treatment on p-type 6H–SiC/SiO2 interface properties were investigated as compared to conventional thermally oxidized devices. It was found that NH3 treatment before oxidation can reduce the SiC/SiO2 interface states and fixed oxide charge. Furthermore, less shift of flatband voltage, and smaller increases of effective oxide charge and interface states during high-field stress were observed for the NH3 pretreated devices. © 2000 American Institute of Physics.published_or_final_versio

Improvement on 1/f noise properties of nitrided n-MOSFET's by backsurface argon bombardment

The 1/f noise properties of nitrided n-MOSFET's bombarded by low-energy (550 eV) argon-ion beam are investigated. It is found that after bombardment, 1/f noise, and its degradation under hot-carrier stress are reduced, and both exhibit a turnaround behavior with bombardment time for a given ion energy and intensity. The physical mechanism involved is probably enhanced interface hardness resulting from bombardment-induced stress relief in the vicinity of the oxide/Si interface. Moreover, from the frequency dependence of the noise, it is revealed that the nitrided devices have a nonuniform trap distribution increasing toward the oxide/Si interface which can be modified by the backsurface bombardment.published_or_final_versio

Interface properties of NO-annealed N2O-grown oxynitride

The oxide/Si interface properties of gate dielectric prepared by annealing N2O-grown oxide in an NO ambient are intensively investigated and compared to those of O2-grown oxide with the same annealing conditions. Hot-carrier stressings show that the former has a harder oxide/Si interface and near-interface oxide than the latter. As confirmed by SIMS analysis, this is associated with a higher nitrogen peak concentration near the oxide/Si interface and a larger total nitrogen content in the former, both arising from the initial oxidation in N2O instead of O2.published_or_final_versio

Dynamic-stress-induced enhanced degradation of 1/f noise in n-MOSFET's

AC-stress-induced degradation of 1/f noise is investigated for n-MOSFET's with thermal oxide or nitrided oxide as gate dielectric, and the physical mechanisms involved are analyzed. It is found that the degradation of 1/f noise under ac stress is far more serious than that under dc stress. For an ac stress of VG = 0 approx. 0.5 VD, generations of both interface state (ΔDit) and neutral electron traps (ΔNet) are responsible for the increase of 1/f noise, with the former being dominant. For another ac stress of VG = 0 approx. VD, a large increase of 1/f noise is observed for the thermal-oxide device, and is attributed to enhanced ΔNet and generation of another specie of electron traps, plus a small amount of ΔDit. Moreover, under the two types of ac stress conditions, much smaller degradation of 1/f noise is observed for the nitrided device due to considerably improved oxide/Si interface and near-interface oxide qualities associated with interfacial nitrogen incorporation.published_or_final_versio

Correlation between hot-carrier-induced interface states and GIDL current increase in N-MOSFET's

Correlation between created interface states and GIDL current increase in n-MOSFET's during hot-carrier stress is quantitatively discussed. A trap-assisted two-step tunneling model is used to relate the increased interface-state density (ADH) with the shift in GIDL current (ΔI d). Results show that under appropriate drain-gate biases, the two-step tunneling is so dominant that A/d is insensitive to temperatures up to about 50 °C. With the help of 2-D device simulation, the locations of the drain region with significant two-step tunneling and the energy levels of the traps involved can be found, with both depending on the drain voltage. From these insights on ADit,A/d and their relation, A Du near the midgap can be estimated, with an error less than 10% as compared to the results of chargepumping measurement on the same transistors. Devices with nitrided gate oxide, different gate-oxide thicknesses and different channel dimensions are also tested to verify the above correlation. © 1998 IEEE.published_or_final_versio

1/f noise in n-channel metal-oxide-semiconductor field-effect transistors under different hot-carrier stresses

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. © 1999 American Institute of Physics.published_or_final_versio

A comparison between NO-annealed O2- and N2O-grown gate dielectrics

Qualities of oxynitrides prepared by annealing O2- and N2O-grown oxides in NO ambient are investigated. Harder oxide/Si interface, less charge trapping and higher charge-to-breakdown characteristics are observed in NO-annealed N2O-grown (N2ONO) oxynitride than NO-annealed O2-grown (O2NO) oxynitride. The involved mechanism lies in higher interfacial nitrogen concentration and total nitrogen content in N2ONO oxynitride than O2NO oxynitride for the same anneal temperature and time.published_or_final_versio

Treatment of stiff thoracic scoliosis by thoracoscopic anterior release combined with posterior instrumentation and fusion

Background. Thoracoscopic anterior release has been shown that it can effectively improve spinal flexibility in animal and human cadaveric studies, and has been advocated for use in patients with scoliosis. This prospective case series aims to investigate the improvement of the spinal flexibility and the effectiveness in deformity correction by anterior thoracoscopic release and posterior spinal fusion. Methods. Eleven patients with stiff idiopathic thoracic scoliosis underwent anterior thoracoscopic release followed by posterior instrumentation. The average number of discs excised was five. Spinal flexibility was assessed by the fulcrum bending technique. Cobb angle before and after the anterior release was compared. Results. The patients were followed for an average of 5.6 years (range 2.2 to 8.1 years). Fulcrum bending flexibility was increased from 39% before the thoracoscopic anterior spinal release to 54% after the release. The average Cobb angle before anterior release was 74° on the standing radiograph and 45° with the fulcrum-bending radiograph. This reduced to 34° on the fulcrum-bending radiograph after the release, and highly corresponded to the 31° measured at the post-operative standing radiograph. Conclusion. It was demonstrated in patients with stiff idiopathic thoracic scoliosis that thoracoscopic anterior spinal release can effectively improve the spinal flexibility and increase the correction of the spinal deformity.published_or_final_versio

Analysis on accuracy of charge-pumping measurement with gate sawtooth pulses

Charge-pumping (CP) measurement is performed on MOSFETs with their gates tied to sawtooth pulses. Influence of both rise time (tr) and fall time (tf) on the CP current of the devices with different channel lengths is investigated at different pulse frequencies. Results show that the dominant mechanism affecting the measurement accuracy is the energy range of interface-trap distribution Dit(E) swept by the gate signal for frequencies below 500 kHz and carrier emission for frequencies above 500 kHz. For frequencies higher than 600 kHz, incomplete recombination could be an additional mechanism when tf is too short. Hence, it is suggested that low frequency is more favorable than high frequency, especially for sawtooth pulses with long tr and short tf , due to little carrier emission and negligible geometric effects even for devices as long as 50 μm. However, if high frequency (e.g. 1 MHz) is required to obtain a sufficiently large S/N ratio in the CP current, sawtooth pulses with equal tr and tf should be chosen for the least carrier emission effect and thus more reliable results on interface-state density, Moreover, for both sawtooth and trapezoidal pulses with a typical amplitude of 5 V, a lower limit of 200 ns for tr and tf is necessary to suppress all the undesirable effects in devices shorter than at least 20 μm.published_or_final_versio