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With helps of advancing CMOS technology, ISFETs have achieved great success. However, CMOS-based ISFETs are also suffering problems of scaling attenuation and threshold voltage offset. These problems mainly result from the architecture used to adapt standard CMOS process. To deal with these, we developed a novel CMOS ISFET configuration, namely, 3D-T-ISFET, by building a truncated architecture to expose CMOS process-inherent TiN thin film as the sensing interface. Due to the electrical conductivity of TiN, the signal from the environment can bypass the sensing dielectric and couple to the transistor effectively through the electrical double layer capacitance. Based on our experiments, as the footprint of $8.5^{2} {\mu } \text{m}$ 2, a 3.21-fold ${\Delta } \text{I}_{D}$ /pH improvement can be achieved by developed 3D-T-ISFET. At the same time, the 3D-T-ISFET has an about 1.65-fold improvement in SNR compared to the traditional 2D-ISFET. Compared to the 2D-ISFET in a state-of-the-art design, therefore, 3D-T-ISFET exhibits a scaling attenuation-free behavior and becomes less vulnerable to the non-idea effects brought by trapped charges. [ABSTRACT FROM AUTHOR]

This work shows a differential rotational thermal piezoresistive resonator (DR-TPR) design, fabrication, and characterization. The resonator uses silicon on insulator (SOI) microelectromechanical systems (SOI MEMS) technology. The sensing of carboxyl-polystyrene beads requires estimating the variation in the frequency of the resonator. It can serve as an alternative enabling technology to detect small molecules having wide implementations in clinical and industrial applications. The resonator uses a negative frequency shift to find the change in the mass due to the chemical absorption of the carboxyl-polystyrene beads on the DR-TPR surface. The method of using DR-TPR can attain label-free detection for many future biomarkers. The use of carboxyl-polystyrene beads to showcase the potential of DR-TPR as a mass sensor for future chemical/biosensing applications is the highlight of the paper. It includes the characterization in different concentrations of immobilization on the resonator surface. The work shows the operation of the resonator in an ionic buffer solution which is crucial for its future applications. The Q value of 80 with differential feedthrough cancellation is measured in phosphate-buffered saline (PBS) using DR-TPR. [ABSTRACT FROM AUTHOR]

As the CMOS-based ion-sensitive field-effect transistor (ISFET) is scaling down to achieve a compact sensing array with high spatial resolution, reduction of sensing layer capacitance attenuates capacitive coupling efficiency of environmental input signals and decreases sensitivity performance. To address this issue, a concept of three-dimensional (3D) sensing structure is proposed and examined in this study. This can increase the sensing layer capacitance for a given footprint area. Based on our designs, a series of 3D sensing structures can be implemented with a standard CMOS foundry service and CMOS-compatible post processes. Our experimental results show that an $8.5^{2}\mu \text{m}^{2}$ footprint design of the 3D sensing structure can obtain approximately 2-fold increase in transconductance compared with a traditional ISFET with the same footprint. This enables pH sensitivity to be improved 1.5-fold in current response and 1.15-fold in voltage response. Therefore, the proposed 3D-structure ISFET can pave the way toward an ISFET sensing array with high sensitivity and high spatial resolution. [ABSTRACT FROM AUTHOR]