Detection of nanoscale biomolecules and accurate analysis of those biomolecules is becoming inevitable day by day due to several new age findings in the field of microbiology. Identification of hundreds of proteins, such as DNA, biotin-streptavidin, S-protein and different kinds of bacteria and virus are crucial to understand any type of peculiar behavior inside a living cell. In addition to this, the pathological results related to COVID-19 shows an analogy among the previously reported SARS and MERS pandemic and the biopsy samples of the lung tissues clearly depicts a lesion in bilateral diffuse alveolar with cellular fibromyxoid exudates. Therefore, the importance of designing more efficient, highly sensitive and low cost biosensors have increased drastically.
Among all, the Field Effect Transistor (FET) based biosensors are of great research interest [1]. They provide several advantages among which CMOS compatibility, high scalability, label-free detection and low-cost production make them a promising candidate for future biosensor applications [2-3]. Significant usage in label free detection of charged bio-analytes has been seen for FET based biosensors [4-7]. The formation of a vertical nanogap with the biosensor has enabled the detection of charge free molecules as well [7-12]. The modulation of the coupling between gate and channel based on different charged/non-charged bio-analytes with varied range of permittivity is the working basis of dielectric modulated FET based biosensor [13]. To cite a few, APTES (K=3.57), Streptavidin (K=2.1), Biotin (K=2.63) [14], food proteins such as Gluten (K=5), Keratin (K=10), Zenin (K=7), Gelatin (K=12) [15] have different permittivity but are non-charged in nature, whereas, among charged bio-analytes, amino acids such as glutamic acid, aspartic acid, arginine, lysine, histidine (K=11-25) [16] are some examples. Moreover, the S-protein of the SARS-CoV-2 virus usually has glycoproteins in it and the dielectric constant of that protein lies in the range of 1-4 [17], similar to biotin or streptavidin. All these biomolecules have been successfully detected by previously reported FET based biosensors. With focus on dielectric modulated biosensing applications, split gate JL MOSFET [18], gate underlap DG MOSFET [19-20], surrounding gate MOSFET [21] have been reported.
In this paper, we have proposed a noise immune dual trench MOSFET (DM DT GE-MOSFET) based biosensor with split fashioned transparent (ITO) outer gate structure coupled with an inner gate. The architecture provides a better control over the channel profile through both exterior and interior gate arrangement. The inclusion of the inner gate enhances the device performance by forming an additional inversion layer. Improved drain current and decent threshold voltage shift makes the device suitable for low power biosensing applications. The biosensing capabilities of the device have been exhibited for various bio-analytes among which DNA, proteins etc. are noticeable ones. Tied-gate, symmetric arrangement with dielectric modulation forms the basis of working for our proposed structure. Cavity has been created on the top and bottom of the device with split-gates in between forming a trench like architecture. Furthermore, the device shows impressive results in terms of RF sensing metric and noise performance.