A novel and patented procedure is described for the sonochemical fabrication of a new class of microelectrode array based sensor with electrode element populations of up to 2 x 10(5) cm(-2). For some years it has been accepted that microelectrode arrays offer an attractive route for lowering minimum limits of detection and imparting stir (convectional mass transport) independence to sensor responses; despite this no commercial biosensors, to date, have employed microelectrode arrays, largely due to the cost of conventional fabrication routes that have not proved commercially viable for disposable devices. Biosensors formed by our sonochemical approach offer unrivalled sensitivity and impart stir independence to sensor responses. This format lends itself for mass fabrication due to the simplicity and inexpensiveness of the approach; in the first instance impedimetric and amperometric sensors are reported for glucose as model systems. Sensors already developed for ethanol, oxalate and a number of pesticide determinations will be reported in subsequent publications.

No abstract

Complex logic chips are almost exclusively assembled in flip chip packaging. This type of assembly complicates traditional debug and circuit modification techniques. Development of new applications and new equipment now enable precise access to the circuitry of flip chip parts. One such application and the equipment developed are being introduced in this article. The technique makes use of optical beam induced current (OBIC) as a way to measure the amount of silicon that is left covering active areas of a flip chip circuit after a trench has been milled in the bulk silicon using a focused ion beam (FIB) system. The apparatus is all contained in one system thus enhancing the throughput of such work. When accessing the circuitry of flip chip parts, it is crucial to be able to locally remove silicon from the backside to within a few microns of the circuitry. This is necessary in order to preserve the integrity of the part and allow access to the circuitry for probe point creation or circuit modification using FIB. OBIC offers a high level of resolution and accuracy in measuring thin layers of bulk silicon in flip chips. In this article we describe the apparatus used, the details of the application, data collected, and a theoretical model developed to confirm the experimental findings.

Sandia is a multiprogram laboratory operated byIntense pulsed high-power ion beams have been demonstrated to produce enhanced surface properties by changes in microstructure caused by rapid heating and cooling of the surface. Additional improvements can be effected by the mixing of a previously deposited thin-film layer (surface alloying or ion beam mixing) into any number of substrate materials. We have conducted surface treatment and alloying experiments with Al, Fe, and Ti-based metals on the RHEPP-1 accelerator (0.8 MV, 20 W, 80 ns FHWM, up to 1 Hz repetition rate) at Sandia National Laboratories. Ions are generated by the MAP gas-breakdown active anode, which can yield a number of different beam species including H, N, and Xe, depending upon the injected gas. Enhanced hardness and wear resistance have been produced by treatment of 44OC stainless steel, and by the mixing of Pt into Ti-6Al-4V alloy. Mixing of a thin-film Hf layer into Al 606 1 -T6 alloy (Al-1 .OMg-O.6Si) has improved its corrosion resistance by as much as four orders of magnitude in electrochemical testing, compared with untreated and uncoated A16061. Experiments are ongoing to further understand the microstructural basis for these surface improvements.

Using a focused ion beam (FIB), secondary electron (SE) imaging of n-wells under oxide from the backside of thinned integrated circuits without electrical bias was accomplished. From the backside, the n-wells were initially observed at a remaining silicon thickness ∼4.5μm, which correlates to the actual implant depth where n and p carrier concentrations are equal. When the wells were FIB imaged, contrast appeared dark relative to the p substrate. During deposition of the oxide film, the n-well brightness changed from dark relative to the p-substrate, to bright. It appears that initially during this deposition step the interaction volume of the beam reached the silicon/oxide interface to create tunneling electrons. This phenomenon dominated the capacitive effect. Then as the film thickness increased the capacitive effect prevailed. The imaging structure is analogous to a Metal-Oxide-Semiconductor (MOS) capacitor. The n- and p-MOS capacitive properties yielded a permanent imaging contrast. At an optimized oxide thickness (130nm), the n-wells appear white relative to the p-substrate with a contrast up to 85% {(Ip-substrate − In-wells)/(Ipsubstrate + In-wells)}.