On the Use of Scalable NanoISFET Arrays of Silicon with Highly Reproducible Sensor Performance for Biosensor Applications

Abstract

As a prerequisite to the development of real label-free bioassay applications, a high-throughput top–down nanofabrication process is carried out with a combination of nanoimprint lithography, anisotropic wet-etching, and photolithography methods realizing nanoISFET arrays that are then analyzed for identical sensor characteristics. Here, a newly designed array-based sensor chip exhibits 32 high aspect ratio silicon nanowires (SiNWs) laid out in parallel with 8 unit groups that are connected to a very highly doped, Π-shaped common source and individual drain contacts. Intricately designed contact lines exert equal feed-line resistances and capacitances to homogenize the sensor response as well as to minimize parasitic transport effects and to render easy integration of a fluidic layer on top. The scalable nanofabrication process as outlined in this article casts out a total of 2496 nanowires (NWs) on a 4 inch p-type silicon-on-insulator (SOI) wafer, yielding 78 sensor chips based on nanoISFET arrays. The sensor platform exhibiting high-performance transistor characteristics in buffer solutions is thoroughly characterized using state-of-the-art surface and electrical measurement techniques. Deploying a pH sensor in liquid buffers after high-quality gas-phase silanization, nanoISEFT arrays demonstrate typical pH sensor behavior with sensitivity as high as 43 ± 3 mV·pH–1 and a device-to-device variation of 7% at the wafer scale. Demonstration of a high-density sensor platform with uniform characteristics such as nanoISFET arrays of silicon (Si) in a routine and refined nanofabrication process may serve as an ideal solution deployable for real assay-based applications.

Electrical Characteristics and pH Response of a Parylene-H Sensing Membrane in a Si-Nanonet Ion-Sensitive Field-Effect Transistor

“…The parylene-H layer deposition process can simply control the formyl group concentration without additional surface modification. Our p-H ISFETs without any surface modification was comparable or even superior to other Si NW-based sensor platforms (see Table 1 ) reported in the literature [ 3 , 16 , 17 , 18 ]. The high sensitivity of p-H ISFETs is attributed to the formation of a high density formyl group (H–C=O) at the surface of the parylene-H/electrolyte, which can release or capture H + [ 9 , 19 ].…”

“…The ion-sensitive field-effect transistor (ISFET) sensor is a potential candidate for future bioassay applications due to its low cost, fast response, high sensitivity and small sensing size. Recently, studies have been conducted on channel materials such as carbon nanotubes and graphene-based materials [ 1 , 2 ]; channel structures such as silicon nanowire (Si NW) arrays, Si-nanonet structure and suspended Si NW [ 3 , 4 , 5 ]. Other approaches to improve the sensing responses have been made by introducing alternative sensing materials instead of SiO 2 as the gate insulator in ISFET.…”

High Aspect Ratio Fin-Ion Sensitive Field Effect Transistor: Compromises toward Better Electrochemical Biosensing

“…Silicon nanowire-field effect transistors (SiNW-FETs) are one of the candidates to be among the building blocks of the next generation molecular diagnostic devices as they offer label-free detection, are miniaturized and thus can be integrated on a microfluidic platform for rapid and low-cost assay [1][2][3] . Their three-dimensional configuration makes them more efficient than planar FETs to detect ultra-low concentrations of analytes due to a better gating effect [4][5][6] . There is a second advantage linked to their geometry.…”

Hybrid Silicon Nanowire Devices and Their Functional Diversity

“…[96] In spite of all the efforts made, top-down routes (Figure 3f-i) usually offer a higher yield and device-to-device reproducibility, making them more favorable for mass production. [32] Several lithography techniques exist to define the nanowires: electron beam lithography (EBL), [97][98][99] focused ion beam (FIB), [100] nanoimprint lithography, [101,102] or local oxidation nanolithography using atomic force microscopy. [32] Several lithography techniques exist to define the nanowires: electron beam lithography (EBL), [97][98][99] focused ion beam (FIB), [100] nanoimprint lithography, [101,102] or local oxidation nanolithography using atomic force microscopy.…”