Lab-on-a-chip based silicon nanowire sensor system for the precise study of chemical reaction-diffusion networks

This work presents the realization of a lab-on-a-chip (LoC) platform based on a SiNW-FET sensor array, a temperature control unit, on-chip temperature sensors, and an on-chip pseudo-reference electrode (pRE) for bio/chemical sensor applications. The SiNW sensors were fabricated based on a mix-and-match "top-down" approach combining electron beam lithography (EBL) and optical lithography on a 4-inch silicon-on-insulator (SOI) wafer (SOITEC, France). The fabrication processes of SiNW-arrays were carried out in a fully CMOS-compatible process. After that, micro-sized temperature sensors based on Pt were fabricated on the wafer close to the SiNW-FET sensors. Up to three on-chip pREs were integrated on the chip surface. Post-CMOS passivation for the temperature sensors based on low-temperature oxidation of titanium was developed to allow the operation of the sensor in liquids and to suppress the interference between the supplied power for the temperature sensor and the liquid-gated SiNW-FETs. For this purpose, a 20 nm thick titanium layer was oxidized at 300deg C in an RTP oven for 90 minutes in pure oxygen. The LoC platform was thoroughly characterized and proofs-of-concept were carried out for the detection of poly-D-lysine (PDL) molecules and a chemical reaction-diffusion network.