Electronic devices in space environments can contain numerous types of oxides and insulators. Ionizing radiation can induce significant charge buildup in these oxides and insulators leading to device degradation and failure. Electrons and protons in space can lead to radiation-induced total-dose effects. The two primary types of radiation-induced charge are oxide-trapped charge and interface-trap charge. These charges can cause large radiation-induced threshold voltage shifts and increases in leakage currents. Two alternate dielectrics that have been investigated for replacing silicon dioxide are hafnium oxides and reoxidized nitrided oxides (RNO). For advanced technologies, which may employ alternate dielectrics, radiation-induced voltage shifts in these insulators may be negligible. Radiation-induced charge buildup in parasitic field oxides and in SOI buried oxides can also lead to device degradation and failure. Indeed, for advanced commercial technologies, the total-dose hardness of ICs is normally dominated by radiation-induced charge buildup in either parasitic field oxides and/or SOI buried oxides. Heavy ions in space can also degrade the oxides in electronic devices through several different mechanisms including single-event gate rupture, reduction in device lifetime, and large voltage shifts in power MOSFETs.

Radiation Effects in MOS Oxides

Analytical application of particle induced X-ray emission

Physics of Amorphous Silicon–Carbon Alloys

Infrared absorption spectra are presented of amorphous Si1−xCx films made by the glow discharge process. Four bands, representing the stretching modes of SiH, CH, and SiC, and the wagging mode of SiCH3, were followed over the entire alloy composition range. It is shown that the compositional dependence of these bands varies in a manner predicted by a model in which Si and C atoms are randomly distributed throughout the film without chemical ordering. The bonded hydrogen content in the films is estimated to be of the order of 20 to 30 at%, depending on composition, with the silicon atoms bonding to a single hydrogen and the carbons bonding predominantly as CH2 and CH3 groups.



Infrarotabsorptionsspektren von amorphen Si1−xCx-Schichten werden mitgeteilt, die durch einen Glimmentladungsprozes hergestellt wurden. Vier Banden, die die Streckungsmoden von SiH, CH, SiC und die „wagging”-Mode von SiCH3 darstellen, lassen sich uber den gesamten Zusammensetzungsbereich der Legierung verfolgen. Es wird gezeigt, das die Zusammensetzungsabhan gigkeit dieser Banden durch ein Modell vorhergesagt wird, in dem die Si- und C-Atome statistisch in der gesamten Schicht ohne chemische Ordnung verteilt sind. Es wird gefunden, das der Anteil an gebundenem Wasserstoff in den Schichten die Grosenordnugn von 20 bis 30 At% hat, je nach Zusammensetzung, wobei die Siliziumatome an isoliertem Wasserstoff gebunden und die Kohlenstoffatome vorwiegend als CH2− und CH3−Gruppen gebunden sind.

Vibrational spectrum of hydrogenated amorphous SiC films

The near‐surface nucleation and crystallization behavior of Ag+ ion‐implanted lithia‐alumina‐silica glasses has been studied. For room‐temperature Ag implants, crystallization of the glass ceramic phase was prevented by dissolution of Ag precipitates and migration of Ag atoms at temperatures below that necessary for formation of the glass ceramic phase. Crystallization was demonstrated after low‐temperature or low‐dose‐rate implantations. Optical spectroscopy was used to monitor the size of colloidal Ag particles and to detect the presence of the crystalline phase. Rutherford backscattering spectroscopy (RBS) was used to obtain the depth distribution of Ag atoms in the glass and thus monitor Ag migration. For samples implanted at room temperature and at relatively high dose rates (∼1 μA/cm2), aggregation of the Ag atoms into colloids occurred during implantation and also during subsequent annealing to temperatures ?350 °C. The RBS spectra indicate some migration of the Ag to the surface at these temperatu...

Aggregation and migration of ion‐implanted silver in lithia‐alumina‐silica glass

The production of SiC in single‐crystal silicon by C12+ implantation to fluences of 1017/cm2‐side followed by annealing has been detected by the characteristic infrared absorption of the TO phonon of SiC. Immediately following room‐temperature implantation and after 20‐min isochronal anneals up to temperatures ≤ 825°C, a previously unreported broad absorption band centered at 700–725 cm−1 is observed. SiC is observed to form at temperatures ≈ 850°C. For anneals ≥ 850°C, most of the broad absorption band shifts into the SiC‐TO phonon absorption band. From the infrared absorption measurements together with the results of He+ backscattering, we conclude that about half of the implanted atoms are incorporated into microregions of SiC which are surrounded by bulk silicon.

FORMATION OF SiC IN SILICON BY ION IMPLANTATION

The nature of the lattice damage produced at room temperature in ion‐implanted intrinsic and n‐type silicon has been studied as a function of 160‐keV O+ ion fluence using electron paramagnetic resonance (EPR). The known EPR spectra observed were the negative divacancy (Si‐G7), the neutral vacancy‐oxygen (Si‐S1), the neutral 4‐vacancy (Si‐P3), and the isotropic resonance at g = 2.0055 which is indicative of amorphous silicon. In addition, a new spectrum, labeled Si‐S2, was observed which may be the negative 4‐vacancy. Concentrations (number/cm2) for the various paramagnetic defects were determined as a function of ion fluence for fluences ranging from 1010 to 1017 O+/cm2. From these measurements we conclude that the lattice damage produced in crystalline silicon by individual ions whose maximum calculated energy density into atomic processes is ≲ 15 eV/A ion consists of simple defects such as observed in electron‐ and neutron‐irradiated silicon. Furthermore, overlap effects in the lattice damage produced b...

Electron paramagnetic resonance of the lattice damage in oxygen‐implanted silicon

A series of experiments has been performed to investigate the response of MOS structures to low-energy radiation. A 10-keV x-ray source was used to irradiate MOS capacitors through a gold/aluminum bilaminate. As expected, the device response when the gold side of the bilaminate faces the device is enhanced strongly with respect to its response when the aluminum side of the bilaminate faces the device. The degree to which the enhanced radiation affects the device response, as determined by the buildup of oxidetrapped charge, depends on the thickness of the gate insulator and the thickness of the capacitor gate in ways similar to those expected from previous work. In addition, striking dependences of the enhanced device response on the energy of the incident radiation, and on the magnitude and direction of the electric field across the gate insulator during the irradiation were observed. These results may provide new insights into the details of the interaction of low-energy radiation with MOS devices.

The Response of MOS Devices to Dose-Enhanced Low-Energy Radiation

We have performed a series of experiments to investigate the response of semiconductor devices to medium-energy x-ray irradiation under conditions in which dose-enhancement effects are very important. We find that the response of MOS capacitors to the same "dose-enhanced" radiation depends not only on the increased dose, but also on the incident radiation spectra, device temperature and processing, and/or oxide thickness and electric field. In many cases, these dependencies cannot be explained simply in terms of existing knowledge of basic mechanisms of radiation effects on MOS devices (for example, electron-hole recombination and hole transport and trapping), or by present Monte Carlo electron/photon transport codes such as the Integrated Tiger Series (ITS). In addition, the response of semiconductor diodes to the "dose-enhanced" radiation appears to be qualitatively different from that of MOS capacitors, and differs markedly in value from the ITS code predictions. These results demonstrate that an improved understanding of semiconductor device response to "enhanced" radiation is needed to assure simulation fidelity of tests of devices to be used in dose-enhancing environments.

Variations in Semiconductor Device Response in a Medium-Energy X-Ray Dose-Enhancing Environment

Volume changes in ion-bombarded single crystals of sapphire and α-quartz have been investigated as functions of ion mass and initial energy and of the energy partitioning into atomic and ionization processes. In addition, channeled proton-induced X-ray measurements were made of displacement damage after ion bombardment. Results indicate an ionization stimulated annealing effect of the radiation damage in sapphire which prevents this material from becoming amorphous even at high ion fluences. In contrast, α-quartz shows no such annealing effect and loses its crystallinity completely at high ion fluences.

W. Beezhold

Papers

FORMATION OF SiC IN SILICON BY ION IMPLANTATION

Electron paramagnetic resonance of the lattice damage in oxygen‐implanted silicon

The Response of MOS Devices to Dose-Enhanced Low-Energy Radiation

Variations in Semiconductor Device Response in a Medium-Energy X-Ray Dose-Enhancing Environment

Effect of Ionizing Radiation on Displacement Damage in Ion-Bmcbarded Single Crystal α-A1 2 O 3 and α-SiO 2