Surface chemical modification induces nanometer scale electron confinement in field effect device.

Design, preparation, and study of physicochemical properties of molecular assemblies are extremely challenging multidisciplinary research fields. Understanding the elementary principles that correlate these properties with molecular level of electronic behavior will enable us to control basic properties of molecule-based compounds as well as of classical semiconductors. In particular, chemical modification of field effect sensor devices where the metal gate is replaced with organic molecular layer, projects a crucial impact upon the electrical properties of the sensor. In these cases it is important to control the effects in order to ensure that the organic gate is optimized for sensing. Here we used fully depleted silicon-on-insulator (SOI) ion sensitive field effect transistor in order to analyze the projection of surface chemical modification on electronic performance. We suggest that surface activation and the application of 3-aminopropyltrimethoxysilane on top of the gate dielectric introduces negative charge at the Si/SiO(2) interface or/and on top of the gate dielectric and consequently an accumulation layer that confines the electrons to the bottom of the SOI channel. The transistor gain postmodification is characteristic of volume inversion, and therefore suggests that, following modification, the channel electrons are confined to SOI thickness of <10 nm. Finally, measurements of pH sensitivity indicate that the pH sensitivity post-UV/O(3) treatment is maximized suggesting that the negative charge is introduced during the activation process, where the density of the negatively charged amphoteric sites maximized.

Standard CMOS Fabrication of a Sensitive Fully Depleted Electrolyte-Insulator-Semiconductor Field Effect Transistor for Biosensor Applications.

Microfabricated semiconductor devices are becoming increasingly relevant for detection of biological and chemical components. The integration of active biological materials together with sensitive transducers offers the possibility of generating highly sensitive, specific, selective and reliable biosensors. This paper presents the fabrication of a sensitive, fully depleted (FD), electrolyte-insulator-semiconductor field-effect transistor (EISFET) made with a silicon-on-insulator (SOI) wafer of a thin 10-30 nm active SOI layer. Initial results are presented for device operation in solutions and for bio-sensing. Here we report the first step towards a high volume manufacturing of a CMOS-based biosensor that will enable various types of applications including medical and environmental sensing.