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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

Direct observation of mobile protons in SiO{sub 2} thin films: Potential application in a novel memory device

Description: In this work we show that annealing of silicon/silicon-dioxide/silicon structures in forming gas (N{sub 2}:H{sub 2}; 95:5) above 500{degrees}C leads to spontaneous incorporation of mobile H{sup +} ions in the buried SiO{sub 2} layer. We demonstrate that, unlike the alkali ions feared as killer contaminants in the early days, the space charge distribution of these mobile protons within the buried oxide layer can be very well controlled and easily rearranged with relatively high speed at room temperature. The hysteresis in the flat band voltage shift provides a unique vehicle to study proton kinetics in silicon dioxide thin films. It is further shown how this effect can be used as the basis for a reliable nonvolatile FET memory device that has potential to be competitive with state-of-the-art Si-based memory technologies. The power of this novel device is its simplicity; it requires few processing steps, all of which are standard in Si integrated-circuit fabrication.
Date: December 31, 1996
Creator: Vanheusden, K.; Warren, W.L. & Fleetwood, D.M.
Partner: UNT Libraries Government Documents Department

Microscopic structure of E{sub {delta}}` center in amorphous SiO{sub 2}: A first principles quantum mechanical investigation

Description: We report the first ab initio quantum mechanical investigation of the structure of the E{sub {delta}}` center in a-SiO{sub 2}. Our calculations suggest that the unpaired electron is shared by only two Si atom, irrespective of the Si cluster size.
Date: March 1, 1997
Creator: Chavez, J.R.; Karna, S.P. & Vanheusden, K.
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

Nature of the green luminescent center in zinc oxide

Description: EPR, optical absorption, and photoluminescence spectroscopies are used to characterize a wide range of different ZnO phosphor powders. A good correlation is generally observed between the 510-nm green emission intensity and the density of paramagnetic isolated oxygen vacancies. Both quantities are found to peak at a free-carrier density of about 1.4x10{sup 18}cm{sup -3}. The green emission intensity can be strongly influenced by free-carrier depletion at the particle surface, especially for small particles and/or low doping. The data suggest that the green PL in ZnO phosphors is due to recombination of electrons in singly occupied oxygen vacancies with photoexcited holes in the valence band.
Date: December 31, 1996
Creator: Vanheusden, K.; Warren, W.L.; Seager, C.H.; Tallant, D.R.; Caruso, J.; Hampden-Smith, M.J. et al.
Partner: UNT Libraries Government Documents Department

The Effect of Near-Interface Network Strain on the Mobility of Protons in SiO{sub 2}

Description: Our data suggest a correlation between near-interface strain in SiO{sub 2} and the ratio of fixed vs. mobile positive charge generated at the interface during forming gas annealing. A model based on first-principles quantum mechanical calculations supports this correlation.
Date: June 17, 1999
Creator: Fleetwood, D.M.; Karna, S.P.; Korambath, P.P.; Kurtz, H.A.; Pugh, R.D.; Shedd, W.M. et al.
Partner: UNT Libraries Government Documents Department

The effects of irradiation and proton implantation on the density of mobile protons in SiO{sub 2} films

Description: Proton implantation into the buried oxide of Si/SiO{sub 2}/Si structures does not introduce mobile protons. The cross section for capture of radiation-induced electrons by mobile protons is two orders of magnitude smaller than for electron capture by trapped holes. The data provide new insights into the atomic mechanisms governing the generation and radiation tolerance of mobile protons in SiO{sub 2}. This can lead to improved techniques for production and radiation hardening of radiation tolerant memory devices.
Date: April 1998
Creator: Vanheusden, K.; Fleetwood, D. M.; Schwank, J. R.; Shaneyfelt, M. R.; Meisenheimer, T. L. & Draper, B. L.
Partner: UNT Libraries Government Documents Department