High-Performance Bidirectional Chemical Sensor Platform Using Double-Gate Ion-Sensitive Field-Effect Transistor with Microwave-Assisted Ni-Silicide Schottky-Barrier Source/Drain

Abstract

This study proposes a bidirectional chemical sensor platform using ambipolar double-gate ion-sensitive field-effect transistors (ISFET) with microwave-assisted Ni-silicide Schottky-barrier (SB) source and drain (S/D) on a fully depleted silicon-on-insulator (FDSOI) substrate. The microwave-assisted Ni-silicide SB S/D offer bidirectional turn-on characteristics for both p- and n-type channel operations. The p- and n-type operations are characterized by high noise resistance as well as improved mobility and excellent drift performance, respectively. These features enable sensing regardless of the gate voltage polarity, thus contributing to the use of detection channels based on various target substances, such as cells, antigen-antibodies, DNA, and RNA. Additionally, the capacitive coupling effect existing between the top and bottom gates help achieve self-amplified pH sensitivity exceeding the Nernst limit of 59.14 mV/pH without any additional amplification circuitry. The ambipolar FET sensor performance was evaluated for bidirectional electrical characteristics, pH detection in the single-gate and double-gate modes, and reliability in continuous and repetitive operations. Considering the excellent characteristics confirmed through evaluation, the proposed ambipolar chemical sensor platform is expected to be applicable to various fields including biosensors. And through linkage with subsequent studies, various medical applications and precision detector operations for specific markers will be possible.

Review–Silicon Based ISFETs: Architecture, Fabrication Process, Sensing Membrane, and Spatial Variation

“…20,57 To address this limitation, numerous studies have been conducted to enhance the sensitivity of ISFETs. [107][108][109][110][111][112][113] A higher sensitivity device is always desirable for both in-vivo and in-vitro systems. Several factors influence the sensitivity of a pH ISFET, including biorecognition layer and the transducer, 7 sensing channel material, 8 resident of hydroxyl group, measuring process and time, 114 processing parameters such as gas flow ratio, 115 fabrication process, 8,[114][115][116][117][118][119] pH sensor and interface unit, 117 parasitic effects (transconductance), 118 total surface-site density (N S ), 34,120,121 presence of oxygen on the surface and hydrogen content in silicon nitride sensitive films, 122 annealing conditions, 115,123 dielectric constant, 123,124 biasing regime of sensors and electrostatic screening of the analyte charges, 125 leakage current, 126,127 drift, 101,[128][129][130] depletion width, 131 capacitance of floating diffusion (FD), 132 scale length with gate oxide thickness.…”

“…Yeong-Ung Kim et al, 2022, 112 presented an ambipolar doublegate ISFET with microwave-assisted Ni-silicide Schottky-barrier (SB) source and Drain (S/D) on a fully depleted silicon-on-insulator ECS Journal of Solid State Science and Technology, 2024 13 047006 (FDSOI) substrate, serving as a bidirectional chemical sensor platform. For both p and n-type channel operations, this S/D offered bidirectional turn-on characteristics.…”

Self-sensitivity amplifiable dual-gate ion-sensitive field-effect transistor based on a high-k engineered dielectric layer

“…Numerous studies have been conducted to exceed the low sensitivity of ISFETs (59.14 mV pH −1 at room temperature), also expressed as the Nernst limit. 7,[12][13][14][15][16][17] In one such study, the dual-gate (DG) sensing mode was realized using a DG structure comprising two gates at the upper and lower part of the ISFET to overcome the Nernst limitation and increase device sensitivity. [17][18][19][20] In the DG structure, the sensitivity of the ISFET is amplified owing to the capacitive coupling effect between the top and bottom gate dielectric layers, and the amplification ratio is governed by the capacitance ratio between the two gate dielectric layers.…”

“…[17][18][19][20] In the DG structure, the sensitivity of the ISFET is amplified owing to the capacitive coupling effect between the top and bottom gate dielectric layers, and the amplification ratio is governed by the capacitance ratio between the two gate dielectric layers. 14,18,19) Meanwhile, the change in the sensitivity extraction method can serve as an effective approach to overcome the sensitivity limit. [21][22][23][24][25] Conventionally, the magnitude of shift (ΔV READ ) in the reference voltage (V READ ) when the sensing membrane is in contact with an analyte having a specific pH value has been widely used as the sensitivity of ISFETs.…”

“…[21][22][23][24][25] Conventionally, the magnitude of shift (ΔV READ ) in the reference voltage (V READ ) when the sensing membrane is in contact with an analyte having a specific pH value has been widely used as the sensitivity of ISFETs. 14,19) This method is intuitive and easy to use for extracting quantitative sensitivity values. However, because it is difficult to overcome the limitation of low sensitivity and a wide range of voltage sweeps is essential for sensing, the power consumption of this method is high.…”