Publications

Abstract not provided.

The potential for aging effects in silicon electronics is a concern for systems with prolonged service lives that contain electronics that must function in extreme radiation environments. A set of laserbased diagnostic techniques is described that is used to provide ongoing awareness of changes in the radiation response of aging discrete and integrated circuits. ©2009 IEEE.

Aging effects in silicon electronics are a concern for systems with prolonged service lives that contain electronics not easily accessible for testing and replacement. Such effects are especially difficult to assess for components that must be exposed to, and function in, transient radiation environments. A methodology has been developed that utilizes electrical parametric and non-destructive laser testing techniques, charge collection microscopy, and controlled-environment storage to permit periodic reassessment of the state of health of such electronics. The use of a scanned, focused laser, charge collection microscopy technique, developed to detect the onset of change and then track these changes in charge collection efficiency with micron resolution, will be described. These results are then used to direct subsequent failure analyses using high-sensitivity, high spatial resolution materials analysis techniques, (such as Time-of-Flight SIMS), in order to identify the underlying material driver of the aging. It will be shown how the results of this methodology are used to create finite-element, charge transport, device models of age-affected devices, and how the time-dependence of the underlying material change is incorporated into the device aging model, so as to predict the future rate, and end-state, of the identified device aging process. Lastly the model is validated using wavelength-dependent charge collection microscopy measurements of the device's response.

Abstract not provided.

Abstract not provided.

High resolution, calibrated ion beam induced charge (IBIC) measurements from integrated circuit test structures have demonstrated that the measured charge collection in a device can exhibit significant change after only a few hundred ions/μm2 exposure, which may easily be exceeded in the initial targeting of a structure. For the purposes of determining a circuit's upset immunity or undamaged charge collection characteristics, such behaviour must be accounted for in evaluating IBIC measurements. This paper examines the influence of low level, ion induced damage on the magnitude of the measured lateral charge collection and also its resulting impact on IBIC image contrast. The lateral charge collection process is first characterised by calculating the amount of charge which diffuses to a collecting junction as a function of carrier diffusion length and the distance between the ion strike and junction edge. The effect of accumulated ion induced damage on lateral charge collection is then incorporated as a decrease in the resultant diffusion length. Calibrated IBIC measurements from the drain of a test FET structure are then explained using this predicted behaviour. © 1998 Elsevier Science B.V.

The nuclear microprobe has proven to be a useful tool in radiation testing of integrated circuits. This paper reviews single event upset and ion beam induced charge collection imaging techniques, with special attention to damage-dependent effects. Comparisons of charge collection measurements with three-dimensional charge transport simulations of charge collection are then presented for isolated p-channel field effect transistors under conducting and non-conducting bias conditions.

Optically targeted, ion microbeams provide a useful means of exposing individual structures within an integrated circuit to ionizing radiation. With this tool, calibrated, low damage, charge collection spectra can be measured from specific circuit structures without preceding ion damage to the structure or surrounding circuitry. This paper presents comparisons of calibrated, low damage, ion microbeam-based charge collection measurements and three-dimensional, charge transport simulations of charge collection for isolated n-and p-channel field effect transistors under conducting and non-conducting bias conditions.

Medical radiotherapy has traditionally relied upon the use of external photon beams and internally implanted radioisotopes as the chief means of irradiating tumors. However, advances in accelerator technology and the exploitation of novel means of producing radiation may provide useful alternatives to some current modes of medical radiation delivery - with reduced total dose to surrounding healthy tissue, reduced expense, or increased treatment accessibility. This paper will briefly overview currently established modes of radiation therapy, techniques still considered experimental but in clinical use and innovative concepts under study that may enable new forms of treatment or enhance existing ones. The potential role of low energy, ion-induced nuclear reactions in radiotherapy applications is examined specifically for the 650 keV d(3He,p)4 He nuclear reaction. This examination will describe the basic physics associated with this reaction's production of 17.4 MeV protons and the processes used to fabricate the necessary materials used in the technique. Calculations of the delivered radiation dose, heat generation, and required exposure times are presented. Experimental data is also presented validating the dose calculations. The design of small, lower cost ion accelerators, as embodied in "nested"-tandem and radio frequency quadrupole accelerators is examined, as is the potential use of high-output 3He and deuterium ion sources. Finally, potential clinical applications are discussed in terms of the advantages and disadvantages of this technique with respect to current radiotherapy methods and equipment. © 1995.

The 6.4 MeV p({sup l5}N,{alpha}{gamma}){sup 12}C resonant nuclear reaction has been used to investigate the role of hydrogen as a contributing factor in the formation of stress-induced voids in very large scale integrated circuit metallizations. Hydrogen profiles were measured from a series of layered structures consisting of aluminum-copper alloy metallizations deposited on borophosphosilicate glass and capped with a variety of commercial passivation materials in order to examine differences in the concentrations and depth distributions of hydrogen within the layered structures.

Traditionally, proton radiotherapy has required the use of high energy proton beams (50-200 MeV) which can penetrate into a patient's body to the site of a tumor that is to be destroyed through irradiation. However, substantial damage is still done to healthy tissue along the path of the incident proton beam, as much as 30% of that done at the tumor site. We propose a new concept for the production and delivery of energetic protons for use in medical radiotherapy, based upon the fact that low energy, ion-induced nuclear reactions can produce radiation products suitable for use in radiotherapy applications. By employing specially fabricated "conduit needles" to deliver beams of energetic ions to selected target materials plugging the end of the needle, ion beam-induced nuclear reactions can be generated at the needle tip, emitting reaction-specific radiation products directly at the tumor site. In this paper, we show that the 13.6 MeV protons produced by the d(3He, p)4He nuclear reaction can deliver a lethal dose (7 krad) of radiation to a 4.4 mm diameter sphere of tissue in only 30 s using a 1 μA, 800 keV 3He ion beam. If also proven clinically feasible, the use of low energy, ion-induced nuclear reactions would allow the utilization of relatively inexpensive, compact, low energy ion accelerators for proton radiotherapy and minimize unintended radiation damage to healthy tissue by providing much greater precision in controlling the irradiated volume. © 1993.

Single Event Upset Imaging utilizes the scanning of a micro-focused MeV ion beams across an integrated circuit to test the upset response of the circuit to energetic heavy ions. Using this technique, the position dependence of logic state upsets, as well as the charge collection efficiency of an integrated circuit, can be directly measured with micron resolution. We present in this paper a review of a series of measurements carried out on the TA670 16K static random access memory chip which display this technique`s capabilities.