Size Independent pH Sensitivity for Ion Sensitive FinFETs Down to 10 nm Width

Gupta, Mihir; Santermans, Sybren; Veloso, A.; Tao, Zheng; Li, Waikin; Hellings, Geert; Lagae, Liesbet; Roy, W. Van; Martens, Koen

doi:10.1109/jsen.2019.2912503

Cited by 12 publications

(8 citation statements)

References 33 publications

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“…In this work, we show that the NP-FET, unlike many other bio-FETs [33], [34], has a unique booster parameter. In particular, the operating point of the NP-FET can be set independently from the effective voltage-change, sensed by the nanopore-gate of the NP-FET, upon a translocation event.…”

Section: Introductionmentioning

confidence: 73%

Boosting the Sensitivity of the Nanopore Field-Effect Transistor to Translocating Single Molecules

et al. 2022

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Nano-scaling of metal-oxide-semiconductor (MOS) fieldeffect transistors (FETs) is exploited to benefit the interdisciplinary field of single-molecule biosensing. While single-molecule DNA sequencing is done successfully by ionic current sensing through nanopores, the unambiguous characterization of more complex single biomolecules, such as fast translocating proteins, remains challenging with existing techniques. However, the nanopore-FET (NP-FET), a device with a nanopore embedded within the channel of the FET, is a promising new device detecting the motion of a molecule through the nanopore based on the transistor's electronic current. This nano-scale FET-based approach enables nextgeneration single-molecule sensing by offering larger signals and hence higher bandwidth, responding to a key challenge of detecting fast translocating molecules, and by offering denser electronic system packing and therefore more parallel sensing. However, the sensitivity of the nanopore-FET reported so far was limited to about 30 %. In this paper, we show that the inherent potential of this hybrid nanofluidic-nanoelectronic device significantly exceeds the initial reportings by demonstrating sensitivity predictions up to 1000 %. Our findings are supported with 3D nanofluidic-nanoelectronic open-source device simulations. Insight in the versatility of the device is provided through geometrical device optimization and demonstration that the device is sensitive to both positively and negatively charged molecules in both n-and p-channel FET configurations. These promising features, together with the immense expertise in MOS fabrication and scaling, offer a path to a highly parallelized and scalable sensor platform for genomics and proteomics.

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Section: Introductionmentioning

confidence: 73%

Boosting the Sensitivity of the Nanopore Field-Effect Transistor to Translocating Single Molecules

et al. 2022

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“…For the simulations to verify the experimental signal, the semiconductor interface trap model was used to describe the pH-dependent oxide–electrolyte charging. It is shown that this interface trap model was equivalent to the site-binding model elsewhere. , The p K a = 4.5 and N s = 4 × 10 13 cm –2 describing the site-binding model were determined from the fit of the experimental pH sensitivity of our FET devices (Section S6).…”

Section: Methodsmentioning

confidence: 99%

“…We based our model of pH-dependent FET sensing on a commercially available technology computer-aided design (TCAD) simulator . Typically, a Poisson–Boltzmann 1:1 electrolyte is described in a TCAD simulator as a customized intrinsic semiconductor wherein the electrons and holes represent the electrolyte anions and cations, respectively. − The biomolecule charge is commonly modeled by a charged ion-permeable layer. A study of nonlinear screening in a commercially available simulator has been reported recently .…”

mentioning

confidence: 99%

“…A study of nonlinear screening in a commercially available simulator has been reported recently . Furthermore, protonation reactions at the gate FET oxide surface have been implemented in TCAD using an interface trap model in studies of pH sensing. − Steric effects due to the finite volume of electrolyte ions have not been considered so far in TCAD and have been accounted for in our TCAD model.…”

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confidence: 99%

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The Significance of Nonlinear Screening and the pH Interference Mechanism in Field-Effect Transistor Molecular Sensors

Santermans

Schanovsky²,

Gupta

et al. 2021

ACS Sens.

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Electrolyte screening is well known for its detrimental impact on the sensitivity of liquid-gated field-effect transistor (FET) molecular sensors and is mostly described by the linearized Debye−Huckel model. However, charged and pH-sensitive FET sensing surfaces can limit the FET molecular sensitivity beyond the Debye−Huckel screening formalism. Pre-existing surface charges can lead to the breakdown of Debye−Huckel screening and induce enhanced nonlinear Poisson−Boltzmann screening. Moreover, the charging of the pH-sensitive surface groups interferes with biomolecule sensing resulting in a pH interference mechanism. With analytical equations and TCAD simulations, we highlight that the Debye−Huckel approximation can underestimate screening and overestimate FET molecular sensitivity by more than an order of magnitude. Screening strengthens significantly beyond Debye− Huckel in the proximity of even moderately charged surfaces and biomolecule charge densities (≥1 × 10 12 q/cm 2 ). We experimentally show the strong impact of both nonlinear screening and the pH interference effect on charge-based biomolecular sensing using a model system based on the covalent binding of single-stranded DNA on silicon FET sensors. The DNA signal increases from 24 mV at pH 7 to 96 mV at pH 3 in 1.5 mM PBS for a DNA density of 7 × 10 12 DNA/cm 2 . Our model quantitatively explains the signal's pH dependence with roughly equal nonlinear screening and pH interference contributions. This work shows the importance of reducing the net charge and the pH sensitivity of the sensing surface to improve molecular sensing. Therefore, tailoring the gate dielectric and functional layer of FET sensors is a promising route to strong silicon FET molecular sensitivity boosts.

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“…A 60 μl silicone flow cell (by Grace Bio-Labs, SKU: 621101-S) was mounted on the sample die and connected to a flow-through true Ag/AgCl electrode (provided by Microelectrodes Inc. product #16-702), which was used to apply gate-source bias (V GS ) through the electrolyte [18]. The semiautomatic measurements were performed using a Keithley 2602 on a nano-probe station (by SUSS Microtech).…”

Section: F Electrical Measurement Setupmentioning

confidence: 99%

Surface Charge Modulation and Reduction of Non-Linear Electrolytic Screening in FET-Based Biosensing

et al. 2021

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We experimentally investigate the influence of non-linear electrolytic screening by the electric double layer (EDL) and its impact on the field-effect transistor (FET) sensitivity to charged (bio)molecules. We use DNA hybridization to a PNA capture probe layer as model system. By co-depositing positively or negatively charged blocker molecules together with the PNA capture probes on the negatively charged SiO 2 surface of the FET, we control the overall surface charge and modulate the strength of local ion concentration within the EDL. We observe a FET signal enhancement of up to 51% when the overall charge including the captured analyte itself swings roughly symmetrically around zero during capture, as confirmed by zeta potential measurements. Surface plasmon resonance measurements rule out a change in captured analyte density as the origin of the enhancement in sensitivity. This confirms that excess screening caused by the large local ion concentration, which increases non-linearly with potential in the EDL, is responsible for a loss in sensitivity in bioFETs with a charged surface. These experimental findings agree with the early theoretical works that find a low surface potential to be desirable for the best bioFET performance.

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Size Independent pH Sensitivity for Ion Sensitive FinFETs Down to 10 nm Width

Cited by 12 publications

References 33 publications

Boosting the Sensitivity of the Nanopore Field-Effect Transistor to Translocating Single Molecules

Boosting the Sensitivity of the Nanopore Field-Effect Transistor to Translocating Single Molecules

The Significance of Nonlinear Screening and the pH Interference Mechanism in Field-Effect Transistor Molecular Sensors

Surface Charge Modulation and Reduction of Non-Linear Electrolytic Screening in FET-Based Biosensing

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