Table 1.

Fabrication process selection frame work of SiNW FET biosensor according to application requirements.

Step	Selection	Possible Options and Their Characteristics
		Option A	Option B
1	Silicon crystallization type	Monocrystalline. Mostly available on SOI wafer, expensive, best electronics properties and uniformity	Polycrystalline. Require deposition and thermal annealing. Cheap, relative good electronic properties, uniformity depend on deposition and annealing process
2	Nanowire designs	Low-concentration doping (<1017 cm−3) yields higher detection sensitivity	High-concentration doping (>1017 cm−3) yields lower detection sensitivity
		Smaller NWs yield higher SVR and hence more sensitivity to charge detection	Larger cross-sectional NWs result in lower SVR and lower detection sensitivity
		Single NW: Theoretically better LODs but prone to large detection signal variation and batch to batch variation	NW arrays: Better reliability but lower limit of detections (LODs)
3	Top-down fabrication routes	Horizontal NWs: High density, good control over quality and uniformity, compatible to packaging and integration but require advanced facility and have high fabrication cost.	Vertical silicon NWs: High aspect ratio, high density, good uniformity and low cost but challenging in regard to integration, packaging and sample delivery
3’	Horizontal SiNW fabrication approaches	Edge transfer lithography: Compatible with standard microfabrication facilities, low cost but lengthy process and high risk of contamination	Nanoimprinting and advanced nanolithography: Require advanced facilities but have low contamination risk and good fabrication throughput and high cost
4	Dielectric insulation	Thermal SiO2: Compatible with standard fabrication process, low intrinsic defects but unstable in long-term measurement in liquid	High-k materials: Additional fabrication complexity and prone to interface defects but excellent durability and stability in long-term measurement
5	Electrical contact formation	Ohmic contacts: Standard process, requires ion-implantation at the contact areas and sensitive to temperature	Silicide contacts: Require stringent control in metal deposition and annealing steps but provide excellent electrical contacts and no requirement for ion-implantation
6	Microfluidics integration	Active microfluidics: Simple fabrication, operation and integration with SiNW FETs but require external power source or pump	Passive microfluidics: Compatible with POC applications, low cost, low or zero energy consumption but careful design and fabrication required to control sample flow and integration with NW FETs
8	Readout	Multi channels: Multiplexed sensing capabilities. Mainly custom built based on the specific specification of the SiNW FETs. Require compromise between resolution/functionality and cost	Single channel: Commercial read out available offering high resolution and universal functionality but bulky, expensive and not compatible for multiplex and POC sensing