Abstract
Silicon nanowire field-effect transistors (SiNW-FET) have been studied as ultra-high sensitive sensors for the detection of biomolecules, metal ions, gas molecules and as an interface for biological systems due to their remarkable electronic properties. “Bottom-up” or “top-down” approaches that are used for the fabrication of SiNW-FET sensors have their respective limitations in terms of technology development. The “bottom-up” approach allows the synthesis of silicon nanowires (SiNW) in the range from a few nm to hundreds of nm in diameter. However, it is technologically challenging to realize reproducible bottom-up devices on a large scale for clinical biosensing applications. The top-down approach involves state-of-the-art lithography and nanofabrication techniques to cast SiNW down to a few 10s of nanometers in diameter out of high-quality Silicon-on-Insulator (SOI) wafers in a controlled environment, enabling the large-scale fabrication of sensors for a myriad of applications. The possibility of their wafer-scale integration in standard semiconductor processes makes SiNW-FETs one of the most promising candidates for the next generation of biosensor platforms for applications in healthcare and medicine. Although advanced fabrication techniques are employed for fabricating SiNW, the sensor-to-sensor variation in the fabrication processes is one of the limiting factors for a large-scale production towards commercial applications. To provide a detailed overview of the technical aspects responsible for this sensor-to-sensor variation, we critically review and discuss the fundamental aspects that could lead to such a sensor-to-sensor variation, focusing on fabrication parameters and processes described in the state-of-the-art literature. Furthermore, we discuss the impact of functionalization aspects, surface modification, and system integration of the SiNW-FET biosensors on post-fabrication-induced sensor-to-sensor variations for biosensing experiments.
Highlights
Introduction published maps and institutional affilDevices for point-of-care testing (POCT) gained attention in recent years due to the societal need for on-demand analysis and a rising market for such devices
We discuss the impact of functionalization aspects, surface modification, and system integration of the silicon nanowires (SiNW)-FET biosensors on post-fabrication-induced sensor-to-sensor variations for biosensing experiments
This is of high importance when it comes to the large-scale fabrication of SiNW-FETs
Summary
Label-free biosensors are analytical devices that transduce the binding of target molecules to their biologically sensitive layer into an electrical signal (Figure 2a). The gate dielectric is in direct contact with a liquid, and a reference electrode that is submerged in the liquid provides the gate voltage for the SiNW-FET sensor. Varying the gate voltage will lead to the electrical current change between the source and drain of the SiNW-FET. A binding event of target molecules to the bio(receptor) layer causes a change in the electrical response of the SiNW-FET (transducer). A SiNW-FET sensor consists of small wires, with a width in the nanometer regime and a length of a few micrometers (Figure 2c). The wires are contacted via extended feed line contacts to source and drain, which have a typical length of a few millimeters (Figure 2d).
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