The impact of nitrogen (N) concentration and distribution on the electrical and reliability properties of rapid-thermally NO-annealed oxides is studied. The use of NO-annealing of thermally grown SiO2 provides an excellent way to isolate the effects of N, since this method allows for the incorporation of varying N profiles in the oxide without a simultaneous increase in dielectric thickness. Results show that the electrical properties of the dielectric under gate and substrate Fowler–Nordheim injection are highly sensitive to the N profile in the dielectric. While interface endurance (ΔDit) is seen to improve monotonically with increasing N concentrations for both +Vg and −Vg, the same is not observed for charge-to-breakdown (QBD) properties. It is found that although QBD improves with NO nitridation under +Vg, it shows a turnaround behavior under −Vg, i.e., for a 10-s NO-annealed oxide the QBD value is improved over control oxide while further nitridation is seen to degrade QBD under −Vg. The presence of bulk N and the nonuniform N distribution in the dielectric is responsible for this behavior.
In this letter, we report on the impact of the suppression of boron diffusion via nitridation of SiO2 on gate oxide integrity and device reliability. SiO2 subjected to rapid thermal nitridation in pure nitric oxide (NO) is used to fabricate thin oxynitride gate dielectrics. Both n+ polycrystalline silicon (polysilicon) gated n-MOS (metal–oxide semiconductor) and p+-polysilicon gated p-MOS devices were subjected to anneals of different times to study the effect of dopant diffusion on gate oxide integrity. As expected, an advanced oxynitride gate dielectric will effectively alleviate the boron-penetration-induced flatband voltage instability in p+-polysilicon gated p-MOS capacitors due to the superior diffusion barrier properties. However, such improvements are observed in conjunction with some degradation of the oxide reliability due to the boron-blocking/accumulation inside the gate dielectric. Results show that even though the oxide quality is slightly degraded for NO-nitrided SiO2 with p+-polysilicon gates, p-MOSFETs (metal–oxide semiconductor field effect transistors) with these dielectrics still show improved interface stability as compared to conventional SiO2 due to the reduced boron penetration into the Si/SiO2 interface and underlying channel region.
We have investigated polarity dependence of dielectric breakdown under constant current stress in scaled S io2 dielectrics. Results show that high-field-induced interface state generation is reduced as oxide thickness scales down and charge-to-breakdown (QBD) for positive gate bias (+V,) increases with decreasing oxide thickness. However, QBD for negative gate bias (-Vg) shows an opposite vend to QBD(+Vg), i.e. QBD(-V~) decreases dramatically with decreasing oxide thickness. Therefore, there is an increased polarity dependence of dielectric breakdown when oxide thickness scales down. A physical model based on the degradation of structural transition layer (STL) and interface is proposed to explain the observed trends in QBD.techniques, i.e. 1050°C rapid-thermal processing (RTP) oxidation and 850°C furnace oxidation, with thicknesses ranging from 42 to 120 A. At the same time, N20-oxides with a similar thickness range were also rapid-thermally grown in pure N 2 0 ambient at 1050°C. Polysilicon was deposited and doped with POCl3, followed by lithography, reactive ion etching and forming gas anneal. QBD was measured by constant current stress. Interface trap density (Dit) was determined from high-frequency C-V (HFCV) and quasi-static C-V (QSCV) measurements. The oxide thicknesses were determined from QSCV measurements. Capacitors with the smallest gate area ( 5~1 0 -~ cm2) were used throughout this study in order to identify only intrinsic breakdown. RESULTS AND DISCUSSION INTRODUCTIONThe reliability of ultrathin gate or tunnel oxides under both injection polarities is an important issue for ULSI technology. Another important issue is the dependence of catastrophic dielectric breakdown on oxide thickness. Much work has been directed toward investigating and modeling of oxide wearout and the impact of thickness scaling on the breakdown mechanism [ 1-61. However, there appears to be several different theories regarding the actual mechanism for dielectric breakdown. Most researchers have developed their model based on a single polarity (usually +V,) measurement results, not much attention has been paid to the investigation of breakdown mechanism under both polarities simultaneously. In this paper, QBD of scaled Si02 under both polarities is studied with thicknesses ranging from 42 to 120 A. The oxides are prepared by using two different techniques, i.e., rapid thermal processing (RTP) oxidation and furnace oxidation. The results clearly show that QBD(+V%) increases with decreasing oxide thickness while QBD(-V~) decreases with decreasing oxide thickness, i.e. greater polarity dependence of dielectric breakdown when oxide thickness scales down. Based on the endurance of the interface and the structural transition layer (STL), we present a model which fully explains the polarity dependence of scaled Si02 breakdown. EXPERIMENTALMOS capacitors with n+-polysilicon gate were fabricated on 5-10 R-cm, p-type Si(100) substrates. Thermal oxide were prepared in dry 0 2 ambient by using two different Figs. 1 and 2 show QBD as a...
In this letter, the dielectric breakdown characteristics of thermal oxides and N2O-based oxynitrides have been studied. A direct correlation was found between dielectric breakdown and the hole current generated within the gate dielectrics. The dependence of dielectric breakdown on oxide thickness was also studied. It was found that both charge-to-breakdown and hole-fluence-to-breakdown for the N2O oxynitrides were higher than those for the thermal oxides throughout the thickness range studied (33–87 Å). The results suggest that N2O oxynitrides can sustain more damage before breakdown and thus have superior dielectric integrity compared to the thermal oxides.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.