Size Independent Sensitivity to Biomolecular Surface Density Using Nanoscale CMOS Technology Transistors

Gupta, Mihir; Santermans, Sybren; Bois, Bert Du; Vos, Rita; Severi, S.; Hellings, Geert; Lagae, Liesbet; Martens, Koen; Roy, W. Van

doi:10.1109/jsen.2020.2987627

Cited by 11 publications

(19 citation statements)

References 33 publications

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“…Each incubation step was followed by ( 2), ( 4) and ( 6) thorough rinsing and end-point measurements using 1.5 mM PBS for both FET as well as SPR. This ensured similar incubation as well measurement conditions for FETs and Biacore 3000 reference measurements [13], [17].…”

Section: Biacore Setup and Protocolmentioning

confidence: 99%

“…The FETs in this work were inversion-mode p-channel devices fabricated completely in a CMOS pilot line [12], [13]. They were fabricated on 300 mm silicon-on-insulator (SOI) wafers (supplied by Soitec) with a 145 nm thick buried oxide (BOX) and 88 nm thick silicon device layer (resistivity ∼12 cm).…”

Section: B Device Fabricationmentioning

confidence: 99%

“…To quantify the amount of PNA/blocker/DNA immobilized on the surface, end-point measurements were done in 1.5 mM PBS running buffer (before and after each sample injection step). This was done to replicate similar conditions as in the end-point FET electrical measurements [13], where 150 mM PBS was used during PNA/blocker/DNA incubation steps (when no FET electrical measurements were being performed) and 1.5 mM PBS was used during FET electrical measurements (after each PNA/blocker/DNA incubation step) as shown in Figure 1. The flow rate for Biacore 3000 was set at 5 μl/min.…”

Section: Biacore Setup and Protocolmentioning

confidence: 99%

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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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Section: Biacore Setup and Protocolmentioning

confidence: 99%

Section: B Device Fabricationmentioning

confidence: 99%

Section: Biacore Setup and Protocolmentioning

confidence: 99%

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

et al. 2021

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“…This potential drop determines the threshold voltage of a liquid-gated FET, 10 T h i s c o n t e n t i s which can be used to monitor the biomolecule signal. 11 In the diffuse layer of the EDL, the concentration of electrolyte ions…”

mentioning

confidence: 99%

“…11 The finFETs were p-channel devices fabricated using CMOS technology as described previously. 11,33 The silicon channel thickness was approximately 20 nm. Fin widths ranged from 60 to 1000 nm, and lengths ranged from 450 to 3000 nm.…”

mentioning

confidence: 99%

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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Analytical Investigation of a Split Double Gate Graded Channel Field Effect Transistor for Biosensing Applications

Singh

Dutta

2022

Silicon

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Size Independent Sensitivity to Biomolecular Surface Density Using Nanoscale CMOS Technology Transistors

Cited by 11 publications

References 33 publications

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

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

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

Analytical Investigation of a Split Double Gate Graded Channel Field Effect Transistor for Biosensing Applications

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