Nano-fin based mercury-sensor for environmental surveillance.

This Nano-Fin-Sensor bases on a lithography-independent technology-process, enabling research on Nano-Sensors without cost-intensive technology-equipment. Background for the sensor described within this paper is the high pollution with mercury of the environment and the lack of cheap, easy to use and portable sensors. The lithography-independent process is based on a "deposition and etch-back" technique defining Nano-Fins. Active sensor-material is a gold-layer, deposited on the fin, increasing resistance being exposed to mercury-vapor due to the process of amalgamation. Regeneration is done by heating-up the gold-layer using the poly-silicon fin as resistance-heating-device driving out the adsorbed mercury. To increase the measurement-accuracy, the sensor is made up of four Nano-Fin-Sensors, connected as Wheatstone-bridge. Two sensors have to be passivated by a mercury diffusion barrier, here a silicon-nitride-layer.

A new cost effective method of planarisation for multiple metal layers in the sub-100 nm-region.

The availability of multiple metal layers has become essential for high-density layouts and economic chip size. The presented paper describes an efficient and low-cost alternative to Chemical-Mechanical-Polishing (CMP). The method uses an auxiliary wafer as a sort of plunger. Starting with a preprocessed wafer, for example from a Complementary-Metal-Oxide-Semiconductor (CMOS) technology, a spin-on glass is applied before the deposition of the first metal layer. Afterwards a second silicon wafer will be covered homogeneously with photo resist and subsequentially coated with aluminum or titanium. This wafer serves as a plunger, while the metal layer protects the photo resist against impression. Whilst the plunger is pressed down on the spin-on glass, the first wafer is cooled down bonding the two wafers together. Separation of the wafers is accomplished by removing the photo resist layer. After the separation step any remaining photo resist as well as the aluminum layer are removed by etching. This process results in a planar surface which is optimally suited for the deposition and structuring of further metal layers which lead to more freedom concerning the complex interconnects in modern analog and digital circuits.