1D silicon nanowires (SiNW) are attractive for charge based DNA sensing applications due to their small size and large surface to volume ratio. An ideal portable biosensor is expected to have repeatable and reliable sensitivity, selectivity, low production cost and small feature size. Instead of using tools such as e-beam that are capital and time intensive, we propose a low cost CMOS self-aligned-double-patterning I-line lithography process to fabricate 60 nm wide SiNW. DNA probes are grafted on a thin dielectric layer that is deposited on top of the SiNW surface. Here we used HfO2 instead of the usual SiO2. Indeed, compared to SiO2, HfO2 has been reported to have higher amount of OH groups on its surface leading to enhanced signal quality.
We also report preliminary biosensor characterizations. After HfO2 functionalization and single-stranded DNA probe grafting onto the SiNWs, the sensors were first put in contact with fluorophore labelled complementary DNA targets in order to test the efficiency of DNA hybridization optically. Then, a sequence of hybridization, de-hybridization and re-hybridization steps was followed by Id-Vg measurements in order to measure the electrical response of the sensors to target DNA as well as recycling capability. After each step, SiNW devices exhibited a threshold voltage shift larger than device-to-device dispersion, showing that both complementary DNA hybridization and de-hybridization can be electrically detected.
These results are very encouraging as they open new frontiers for heterogeneous integration of liquid interacting array of nano sensors with CMOS circuits to fabricate a complete lab on chip.
Ganesh Jayakumar, Maxime Legallais, Per-Erik Hellström, Mireille Mouis, Valérie Stambouli, Céline Ternon, and Mikael Östling, "Fabrication and characterization of high-K dielectric integrated silicon nanowire sensor for DNA sensing application
(Conference Presentation)," Proc. SPIE 9930, Biosensing and Nanomedicine IX, 99300Q (Presented at SPIE Nanoscience + Engineering: August 30, 2016; Published: 3 November 2016); https://doi.org/10.1117/12.2237350.5164183648001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon