Silicon nanowire field-effect transistor (SiNW-FET) sensors possess the ability of rapid response, real-time, and label-free detection with high sensitivity and selectivity in the analysis of charged molecules. Their nano-scale size makes them well suited for ultralow detection of charged molecules, but also brings the uniformity fabrication challenging, thus limiting their large-scale application. By a horizontal control approach, highly controllable silicon nanowires arrays at the top of the silicon-on-insulator (SOI) wafer (T-SiNW) were developed in our previous work. To further improve the device uniformity, here a novel SiNW fabricated approach was carefully designed by the combination of horizontal and vertical control. The new silicon nanowires appeared at the bottom of the top silicon layer (B-SiNW). The B-SiNW has a relatively low requirement on the fabrication process and better device uniformity compared to T-SiNW. These improvements resulted in the B-SiNW device with a lower current fluctuation (4.1 nA with 5.1% variations) in the flowing liquid, compared to the T-SiNW device (4.4 nA with 11% variations). Further, in quantitative detection of 40 ng/mL MMP-9, the B-SiNW sensors provided larger signals and lower fluctuation (normalized average response value: 0.57 with 4.2% variations), compared to the T-SiNW sensors (0.41 with 12.1% variations), thus indicating a more accurate bio-analysis application of the B-SiNW sensor. This work advances the nanowire sensor technology a step closer toward large-scale application to create stable sensing platforms in disease diagnosis and monitoring.

This paper presents a wafer-level and highly controllable fabrication technology for silicon nanowire field-effect transistor (SiNW-FET arrays) on (111) silicon-on-insulator (SOI) wafers. Herein, 3, 000 SiNW FET array devices were designed and fabricated on 4-inch wafers with a rate of fine variety of more than 90% and a dimension deviation of the SiNWs of less than ± 20 nm in each array. As such, wafer-level and highly controllable fabricated SiNW FET arrays were realized. These arrays showed excellent electrical properties and highly sensitive determination of pH values and nitrogen dioxide. The high-performance of the SiNW FET array devices in liquid and gaseous environments can enable the detection under a wide range of conditions. This fabrication technology can lay the foundation for the large-scale application of SiNWs.

An approach for the wafer-level synthesis of size- and site-controlled amorphous silicon nanowires (α-SiNWs) is presented in this paper. Microscale Cu pattern arrays are precisely defined on SiO₂ films with the help of photolithography and wet etching. Due to dewetting, Cu atoms shrink to the center of patterns during the annealing process, and react with the SiO₂ film to open a diffusion channel for Si atoms to the substrate. α-SiNWs finally grow at the center of Cu patterns, and can be tuned by varying critical factors such as Cu pattern volume, SiO₂ thickness, and annealing time. This offers a simple way to synthesize and accurately position a SiNW array on a large area.