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Comparative hot carrier induced degradation in 0.25 {micro}m MOSFETs with H or D passivated interfaces

Description: Hot electron induced degradation in 0.25 {micro}m, n-channel MOSFETs annealed in H{sub 2} or D{sub 2} containing atmospheres is reported. Threshold voltage and channel transconductance variations correlate with the growth of the interface state density. The spectral density of the stress induced interface states in the Si bandgap does not depend upon the anneal gas but the transistor lifetime (for a 20% transconductance variation) is {approximately} 40 times shorter for H{sub 2} as opposed to D{sub 2} annealed devices.
Date: March 1, 1997
Creator: Autran, J.L.; Devine, R.A.B.; Warren, W.L. & Vanheusden, K.
Partner: UNT Libraries Government Documents Department

Retention and Switching Kinetics of Protonated Gate Field Effect Transistors

Description: The switching and memory retention time has been measured in 50 {micro}m gatelength pseudo-non-volatile memory MOSFETs containing, protonated 40 nm gate oxides. Times of the order of 3.3 seconds are observed for fields of 3 MV cm{sup {minus}1}. The retention time with protons placed either at the gate oxide/substrate or gate oxide/gate electrode interfaces is found to better than 96% after 5,000 seconds. Measurement of the time dependence of the source-drain current during switching provides clear evidence for the presence of dispersive proton transport through the gate oxide.
Date: June 27, 2000
Creator: Devine, R. A. B. & Herrera, Gilbert V.
Partner: UNT Libraries Government Documents Department

Retention and switching kinetics of protonated gate field effect transistors

Description: The switching and memory retention time has been measured in 50 {micro}m gatelength pseudo-non-volatile memory MOSFETS containing, protonated 40 nm gate oxides. Times of the order of 3.3 seconds are observed for fields of 3 MV cm{sup {minus}1}. The retention time with protons placed either at the gate oxide/substrate or gate oxide/gate electrode interfaces is found to better than 96{percent} after 5,000 seconds. Measurement of the time dependence of the source-drain current during switching provides clear evidence for the presence of dispersive proton transport through the gate oxide.
Date: May 23, 2000
Creator: DEVINE,R.A.B. & HERRERA,GILBERT V.
Partner: UNT Libraries Government Documents Department

Near interface oxide degradation in high temperature annealed Si/SiO{sub 2}/Si structures

Description: Degradation of 430 nm thick SiO{sub 2} layers in Si/SiO{sub 2}/Si structures which results from high temperature annealing (1320 C) has been studied using electron spin resonance, infra-red and refractive index measurements. Large numbers of oxygen vacancies are found in a region {le}100 nm from each Si/SiO{sub 2} interface. Two types of paramagnetic defects are observed following {gamma} or x-irradiation or hole injection. The 1106 cm{sup {minus}1} infra-red absorption associated with O interstitials in the Si substrate is found to increase with annealing time. The infra-red and spin resonance observations can be explained qualitatively and quantitatively in terms of a model in which oxygen atoms are gettered from the oxide into the under or overlying Si, the driving force being the increased O solubility limit associated with the anneal temperature.
Date: December 31, 1993
Creator: Devine, R. A. B.; Mathiot, D.; Warren, W. L. & Fleetwood, D. M.
Partner: UNT Libraries Government Documents Department

Electron induced depassivation of H and D terminated Si/SiO{sub 2} interfaces

Description: The authors have performed electron spin resonance and electrical measurements on SiO{sub 2}/Si structures subjected to anneals in 5% H{sub 2}/N{sub 2} or 5% D{sub 2}/N{sub 2} gases and subsequently injected with electrons using corona ions and ultra-violet radiation. Threshold voltage and transconductance measurements have also been made on 0.25 {micro}m metal-oxide-semiconductor transistors subjected to 400 C anneals in the same gases and subsequently aged by hot electron injection. The electrical data on SiO{sub 2}/Si structures indicates that the density of interface states increases as a result of electron injection but that there are only minor differences between H and D passivated interfaces. The data on P{sub b}, trivalent Si dangling bond, centers at the same interfaces observed by electron spin resonance is insufficiently accurate to enable them to observe any significant differences. The hot electron injection experiments on transistors, consistent with other authors, indicate that, for the limited number of measurements they have made, the transistor aging resulting from the generation of interface states is significantly reduced for devices annealed in the D containing gas as compared to those annealed in the H containing gas. The origins of some potential differences in annealing behavior between the SiO{sub 2}/Si structures and the 0.25 {micro}m transistors are suggested.
Date: February 1, 1997
Creator: Devine, R.A.B.; Mourrain, C.; Bouzid, M.J.; Warren, W.L. & Vanheusden, K.
Partner: UNT Libraries Government Documents Department

Nonvolatile field effect transistors based on protons and Si/SiO{sub 2}Si structures

Description: Recently, the authors have demonstrated that annealing Si/SiO{sub 2}/Si structures in a hydrogen containing ambient introduces mobile H{sup +} ions into the buried SiO{sub 2} layer. Changes in the H{sup +} spatial distribution within the SiO{sub 2} layer were electrically monitored by current-voltage (I-V) measurements. The ability to directly probe reversible protonic motion in Si/SiO{sub 2}/Si structures makes this an exemplar system to explore the physics and chemistry of hydrogen in the technologically relevant Si/SiO{sub 2} structure. In this work, they illustrate that this effect can be used as the basis for a programmable nonvolatile field effect transistor (NVFET) memory that may compete with other Si-based memory devices. The power of this novel device is its simplicity; it is based upon standard Si/SiO{sub 2}/Si technology and forming gas annealing, a common treatment used in integrated circuit processing. They also briefly discuss the effects of radiation on its retention properties.
Date: March 1, 1997
Creator: Warren, W.L.; Vanheusden, K.; Fleetwood, D.M.; Schwank, J.R.; Winokur, P.S.; Knoll, M.G. et al.
Partner: UNT Libraries Government Documents Department

A Nonvolatile MOSFET Memory Device Based on Mobile Protons in SiO(2) Thin Films

Description: It is shown how mobile H{sup +} ions can be generated thermally inside the oxide layer of Si/SiO{sub 2}/Si structures. The technique involves only standard silicon processing steps: the nonvolatile field effect transistor (NVFET) is based on a standard MOSFET with thermally grown SiO{sub 2} capped with a poly-silicon layer. The capped thermal oxide receives an anneal at {approximately}1100 C that enables the incorporation of the mobile protons into the gate oxide. The introduction of the protons is achieved by a subsequent 500-800 C anneal in a hydrogen-containing ambient, such as forming gas (N{sub 2}:H{sub 2} 95:5). The mobile protons are stable and entrapped inside the oxide layer, and unlike alkali ions, their space-charge distribution can be controlled and rapidly rearranged at room temperature by an applied electric field. Using this principle, a standard MOS transistor can be converted into a nonvolatile memory transistor that can be switched between normally on and normally off. Switching speed, retention, endurance, and radiation tolerance data are presented showing that this non-volatile memory technology can be competitive with existing Si-based non-volatile memory technologies such as the floating gate technologies (e.g. Flash memory).
Date: March 2, 1999
Creator: Vanheusden, K.; Warren, W.L.; Devine, R.A.B.; Fleetwood, D.M.; Draper, B.L. & Schwank, J.R.
Partner: UNT Libraries Government Documents Department

Hydrogen diffusion and chemistry during the annealing-induced generation of mobile protons in the oxide layer of Si/SiO{sub 2}/Si capacitors

Description: In a number of recent studies the generation of mobile protons in the buried oxide of SOI materials and in thermal oxide buried underneath a poly-Si layer has been discussed. The protons are found to be stable and can be easily rearranged by applying an electric field. The details of the hydrogen reactions leading to the generation of the mobile H{sup +} are still under investigation. In a recent work a dynamic equilibrium model was presented. The forward reaction dominates above {approximately} 500 C and the resulting H{sup +} is mobile and entrapped inside the SiO{sub 2}. The electron is donated to the Si. The H{sup 0} is likely to be formed through H{sub 2} + K {Leftrightarrow} HK + H{sup 0}, where K is a cracking site. In the same work it was shown that the reactive hydrogen species enter the oxide from the device edges. Hence, the amount of the reactive species reaching the oxide by diffusion through the Si overlayer is negligible. These results seem to contradict earlier studies where it is shown that hydrogen can easily diffuse through the top Si layer under the given experimental conditions. The authors present here new details on hydrogen diffusion and chemistry during the protonation anneal that may offer an explanation for the hydrogen diffusion paradox. The new findings suggest that reactions at the ambient/SiO{sub 2} interface play a key role.
Date: September 1, 1998
Creator: Vanhuesden, K.; Devine, R.A.B.; Fleetwood, D.M. & Warren, W.L.
Partner: UNT Libraries Government Documents Department

Reliability implications of defects in high temperature annealed Si/SiO{sub 2}/Si structures

Description: High-temperature post-oxidation annealing of poly-Si/SiO{sub 2}/Si structures such as metal-oxide-semiconductor capacitors and metal-oxide-semiconductor field effect transistors is known to result in enhanced radiation sensitivity, increased 1/f noise, and low field breakdown. The authors have studied the origins of these effects from a spectroscopic standpoint using electron paramagnetic resonance (EPR) and atomic force microscopy. One result of high temperature annealing is the generation of three types of paramagnetic defect centers, two of which are associated with the oxide close to the Si/SiO{sub 2} interface (oxygen-vacancy centers) and the third with the bulk Si substrate (oxygen-related donors). In all three cases, the origin of the defects may be attributed to out-diffusion of O from the SiO{sub 2} network into the Si substrate with associated reduction of the oxide. The authors present a straightforward model for the interfacial region which assumes the driving force for O out-diffusion is the chemical potential difference of the O in the two phases (SiO{sub 2} and the Si substrate). Experimental evidence is provided to show that enhanced hole trapping and interface-trap and border-trap generation in irradiated high-temperature annealed Si/SiO{sub 2}/Si systems are all related either directly, or indirectly, to the presence of oxygen vacancies.
Date: August 1, 1994
Creator: Warren, W. L.; Fleetwood, D. M.; Shaneyfelt, M. R.; Winokur, P. S.; Devine, R. A. B.; Mathiot, D. et al.
Partner: UNT Libraries Government Documents Department