Yi-Ting Lin

Immobilization of enzyme and antibody on ALD-HfO2-EIS structure by NH3 plasma treatment

Thin hafnium oxide layers deposited by an atomic layer deposition system were investigated as the sensing membrane of the electrolyte-insulator-semiconductor structure. Moreover, a post-remote NH3 plasma treatment was proposed to replace the complicated silanization procedure for enzyme immobilization. Compared to conventional methods using chemical procedures, remote NH3 plasma treatment reduces the processing steps and time. The results exhibited that urea and antigen can be successfully detected, which indicated that the immobilization process is correct.

Light-Immune pH Sensor with SiC-Based Electrolyte--Insulator--Semiconductor Structure

An electrolyte–insulator–semiconductor (EIS) structure with high-band-gap semiconductor of silicon carbide is demonstrated as a pH sensor in this report. Two different sensing membranes, i.e., gadolinium oxide (Gd2O3) and hafnium oxide (HfO2), were investigated. The HfO2 film deposited by atomic layer deposition (ALD) at low temperature shows high pH sensing properties with a sensitivity of 52.35 mV/pH and a low signal of 4.95 mV due to light interference. The EIS structures with silicon carbide can provide better visible light immunity due to its high band gap that allows pH detection in an outdoor environment without degradation of pH sensitivity.

Nano-IGZO layer for EGFET in pH sensing characteristics

In-Ga-Zn-O (IGZO) was widely applied in the substrate of TFT to replace a-Si in recent year. In this study, IGZO layer with thickness of 70 nm is first proposed as a pH sensing membrane directly on P-type Si substrate acting as an extended gate of conventional extended-gate field-effect Transistor (EGFET). Material criteria of extended gate electrode are low resistance and high capacitance. Therefore, Ar/O2 ratio was modified in the rf sputtering with IGZO target. Post deposition anneal was also performed to check the sheet resistance and pH sensing performance. EGFETs were measured in standard pH buffer solution by using B1500A and constant voltage constant current (CVCC) circuit. Similar IDS-VGS curves including transconductance (Gm) and substrate swing (S.S.) are obtained in various sputtering conditions of IGZO compared to commercial NMOSFET in CD4007. pH application range is only between pH 2 to pH 10. IGZO-EGFET prepared by Ar/O2 ambience of 24/1 in sputtering can have a sensitivity of 59.5 mV/pH. Lower sensitivity and linearity can be observed in the samples with RTA treament at higher temp and in O2 ambience. N2 anneal at 500°C can be used to improve pH sensing performance for IGZO-EGFET prepared by Ar/O2 ambience of 20/5 in sputtering. Nano-IGZO layer is verified to be the sensing membrane in EGFET to have a high sensitivity of 59.5 mV/pH for the first time. More studies on enlargement pH application range and minimization of non-ideal effect still need to be investigated.

VERTICAL SILICON NANOWIRES WITH ATOMIC LAYER DEPOSITION WITH HfO2 MEMBRANE FOR pH SENSING APPLICATION

Vertical silicon nanowire (SiNW) platforms are candidates for use in ultrasensitive biosensors, with surface-to-volume ratio higher than one-dimensional SiNW. In this paper, a vertical SiNW electrolyte–insulator–semiconductor (EIS) structure with an ALD-HfO2 sensing membrane is proposed for use in a hydrogen ion sensor. Hafnium dioxide is used as the sensing membrane, which was deposited on the surface of the vertical SiNW structure by atomic layer deposition. The sensing properties were examined using a HP4284A high-precision LCR analyzer. A linear relationship was found between the flatband voltage shift and the hydrogen ion concentration. Comparing with different diameters of SiNW, the sensitivity with diameter of 200 nm was slightly higher than 100 nm. A post-deposition rapid thermal annealing (RTA) was utilized to optimize the sensing properties, and the sensitivity was increased to 51.07 mV/pH.

Programming a nonvolatile memory-like sensor for KRAS gene sensing and signal enhancement.

A programmable field effect-based electrolyte-insulator-semiconductor (EIS) sensor constructed with a nonvolatile memory-like structure is proposed for KRAS gene DNA hybridization detection. This programmable EIS structure was fabricated with silicon oxide (SiO2)/silicon nitride (Si3N4)/silicon oxide on a p-type silicon wafer, namely electrolyte-oxide-nitride-oxide-Si (EONOS). In this research, voltage stress programming from 4 to 20V was applied to trigger holes confinement in the nitride-trapping layer that, consequently, enhances the DNA attachment onto the sensing surface due to additional electrostatic interaction. Not solely resulting from the higher DNA load, the programming may affect the orientation of the DNA that finally contributes to the change in capacitance. Findings have shown that a higher voltage program is able to increase the total capacitance and results in ~3.5- and ~5.5-times higher sensitivities for a series of concentrations for complementary DNA and wild type versus mutant DNA hybridization detection, respectively. Overall, it has been proven that the voltage program on the nonvolatile memory-like structure of EONOS is a notable candidate for genosensor development, scoping the diagnosis of a single nucleotide polymorphism (SNP)-related disease.

Ultra-high scanning speed chemical image sensor based on light addressable potentiometric sensor with analog micro-mirror

In chemical image sensor, spatial resolution and scanning speed are the most important factors which may need to optimize and trade off. Before the minimization of spatial resolution, scanning speed of system needs to be improved to have an image in a short time within few seconds. In this study, ultra-high scanning speed of light addressable potentiometric sensor (LAPS) could be achieved by means of the combination of laser diode and single analog micro-mirror in light source. In the constant bias operation, an U-shape of pH solution can be detected within 8.5 sec for 14×121 points in the area of 3.2 mm×6.12 mm by using 5 kHz of ac signal in laser diode. The image resolution of the present LAPS system with 10 μm-thick Si3N4/3 nm-thick SiO2 on 500 μm-thick silicon wafer is 0.0116 mm2 which could be further improved by LAPS structure optimization with thinner substrate. A chemical image sensor with ultra-high scanning speed is demonstrated by the application of analog micro-mirror for LAPS.

Characterization of body effect of Au-EGFET for KRAS gene detection

The sensing properties of Au-EGFET with body effect for DNA detection were first investigated in this study. The body effect means different substrate bias in CMOS circuit operation without common ground. With positive VBS of 1V, more shift of ID-VG curve could be a good index of DNA hybridization and concentration. It could be explained be the electric field induced counter ion effect. This measured technique can be used to enhance the sensing signal and improve the limit of detection (LOD).

1.2.1 Urea Biosensor Using NH3 Nitrided Amine Groups on Flexible Substrate

In this study, indium tin oxide (ITO) layers were deposited on polyethylene terephthalate (PET) substrates (ITO/PET) as a sensing membrane. In order to generate the amine groups on the surface for urease immobilization, NH3 plasma was used with RF power of 100 W for various times. The pH sensitivities of ITO/PET electrodes treated without and with NH3 plasma for 3 and 6 min were all around 51±4 mV/pH. However, the pH sensitivities of the samples treated with NH3 plasma for 9 min were slightly reduce to 45±5 mV/pH. In addition, the urea sensitivities of ITO/PET EGFET can be increased from 20.7 to 43.3 mV/pCurea by NH3 plasma from 3 to 9 min.