Tung-Ming Pan

Excellent frequency dispersion of thin gadolinium oxide high-k gate dielectrics

In this letter, we reported a high-k gadolinium oxide (Gd2O3) gate dielectric formed by reactive rf sputtering. It is found that the Gd2O3 gate dielectric film exhibits excellent electrical properties such as low leakage current density, high breakdown voltage, and almost no hysteresis and frequency dispersion in C‐V curves comparable to that of HfO2 film. This indicates that postprocessing treatments can reduce a large amount of interface trap and can passivate a large amount of trapped charge at defect sites.

Structural and electrical characteristics of thin erbium oxide gate dielectrics

A high-k erbium oxide thin film was grown on silicon substrate by reactive rf sputtering. It is found that the capacitance value of Er2O3 gate dielectric with TaN metal gate annealed at 700°C is higher compared to other annealing temperature and exhibits a lower hysteresis voltage as well as interface trap density in C-V curves. They also show negligible charge trapping under high constant voltage stress. This phenomenon is attributed to a rather well-crystallized Er2O3 and the decrease of the interfacial layer and Er silicate thickness observed by x-ray diffraction and x-ray photoelectron spectroscopy, respectively.

Real-Time and Label-Free Detection of the Prostate-Specific Antigen in Human Serum by a Polycrystalline Silicon Nanowire Field-Effect Transistor Biosensor

In this research, we used a polycrystalline silicon nanowire field-effect transistor (poly-Si NWFET) as a biosensor that employs the sidewall spacer technique instead of an expensive electron beam lithography method. When compared with commercial semiconductor processes, the sidewall spacer technique has the advantages of simplicity and low cost. In this study, we employed a novel poly-Si NWFET device for real-time, label-free, and ultrahigh-sensitivity detection of prostate-specific antigen (PSA) in human serum. Since serum proteome is very complex containing high levels of salts and other interfering compounds, we hereby developed a standard operating procedure for real-sample pretreatment to keep a proper pH value and ionic strength of the desalted serum and also utilized Tween 20 to serve as the passivation agent by surface modification on the NWFET to reduce nonspecific binding for medical diagnostic applications. We first modified 3-aminopropyltriethoxysilane on the surface of a poly-Si nanowire device followed by glutaraldehyde functionalization, and the PSA antibodies were immobilized on the aldehyde terminal. While PSA was prepared in the buffers to maintain an appropriate pH value and ionic strength, the results indicated that the sensor could detect trace PSA at less than 5 fg/mL in a microfluidic channel. The novel poly-Si NWFET is developed as a diagnostic platform for monitoring prostate cancer and predicting the risk of early biochemical relapse.

High-k cobalt-titanium oxide dielectrics formed by oxidation of sputtered Co/Ti or Ti/Co films

High-k cobalt–titanium oxide (CoTiO3) film was formed by directly oxidizing sputtered Co/Ti or Ti/Co films. Al/CoTiO3/Si3N4/Si capacitor structures were fabricated and measured. Excellent electrical properties with an effective dielectric constant (i.e., k value) as high as 40 have been achieved for a CoTiO3 gate dielectric with a buffer layer. The metal–oxide thus appears to be a very promising high-k gate dielectric for future ultralarge scale integrated devices.

Forming-free resistive switching behavior in Nd2O3, Dy2O3, and Er2O3 films fabricated in full room temperature

In this study, we reported the forming-free resistive switching behavior in the Ru/RE2O3/TaN (RE = Nd, Dy, and Er) memory devices using thin Nd2O3, Dy2O3, and Er2O3 films fabricated with full room temperature process. The dominant conduction mechanisms of the Ru/RE2O3/TaN devices in the low-resistance state and high-resistance state are Ohmic behavior. The Ru/Dy2O3/TaN memory device exhibited high resistance ratio, nondestructive readout, reliable data retention, and good endurance. Ru/Dy2O3/TaN memory device has a great potential for the application in nonvolatile resistive switching memory.

Structural and electrical properties of neodymium oxide high-k gate dielectrics

In this letter, the authors reported a high-k neodymium oxide gate dielectric grown by reactive rf sputtering. It is found that the Nd2O3 gate dielectric after annealing at 700°C exhibits excellent electrical properties such as low equivalent oxide thickness, high electric breakdown field, and almost no hysteresis and frequency dispersion in C-V curves. This indicates that annealing at 700°C treatment can prevent the interfacial layer and silicate formation, reduce a large amount of interface trap, and passivate a large amount of trapped charge at defect sites.

Integrating solid-state sensor and microfluidic devices for glucose, urea and creatinine detection based on enzyme-carrying alginate microbeads

A solid-state sensor embedded microfluidic chip is demonstrated for the detection of glucose, urea and creatinine in human serum. In the presented device, magnetic powder-containing enzyme-carrying alginate microbeads are immobilized on the surface of an electrolyte-insulator-semiconductor (EIS) sensor by means of a step-like obstacle in the microchannel and an external magnetic force. The sample is injected into the microchannel and reacts with the enzyme contained within the alginate beads; prompting the release of hydrogen ions. The sample concentration is then evaluated by measuring the resulting change in the voltage signal of the EIS sensor. The reaction time and alginate bead size are optimized experimentally using a standard glucose solution. The experimental results show that the device has a detection range of 2-8mM, 1-16mM and 10(-2)-10mM for glucose, urea and creatinine, respectively. Furthermore, it is shown that the device is capable of sequentially measuring all three indicators in a human serum sample. Finally, it is shown that the measured values of the glucose, urea and creatinine concentrations obtained using the device deviate from those obtained using a commercial kit by just 5.17%, 6.22% and 13.53%, respectively. This method can be extended to sequentially measure multiple blood indicators in the sample chip by replacing different types of enzyme in alginate bead and can address the enzyme preservation issue in the microfluidic device. Overall, the results presented in this study indicate that the microfluidic chip has significant potential for blood monitoring in point-of-care applications.

A high-k Y2O3 charge trapping layer for nonvolatile memory application

In this letter, a silicon-oxide-high-k-oxide-silicon memory structure using a high-k Y2O3 film as the charge trapping layer is reported for nonvolatile memory application. From x-ray photoelectron spectroscopic analysis, we found that the Y2O3 layer formed after annealing at 700°C for 30s. When using channel hot electron injection for charging and band-to-band hot hole for discharging, the high-k Y2O3 memories exhibited large threshold voltage shifting (memory window of 2.3V), excellent data retention (charge loss of 8% at room temperature), and good endurance characteristics (program/erase cycles up to 105) because of the higher probability for trapping the charge carrier due to the formation of a well-crystallized Y2O3 structure.

Structural Properties and Electrical Characteristics of Praseodymium Oxide Gate Dielectrics

Structural properties and electrical characteristics of praseodymium oxide gate dielectrics grown on Si substrate by reactive rf sputtering were investigated. The structure, composition, and interfacial characteristics of these dielectrics were examined using X-ray diffraction and X-ray photoelectron spectroscopy. It is found that Pr 2 O 3 gate dielectric with TaN metal gate annealed at 700°C exhibits a higher capacitance value (∼450 pF, EOT = 2.41 nm) and lower flatband voltage (∼-0.5 V) in C-V curves, and shows the leakage value of ∼5 X 10 -7 A/cm 2 at a bias of 2 V. They also show negligible charge trapping under high constant voltage stress. This phenomenon is attributed to a rather well-crystallized Pr 2 O 3 and the decrease of the interfacial layer and Pr silicate thickness.

Physical and Electrical Properties of Yttrium Oxide Gate Dielectrics on Si Substrate with NH3 Plasma Treatment

We report on the physical properties and electrical characteristics of Y 2 O 3 gate oxides grown on silicon substrates with NH 3 plasma treatment by reactive radio-frequency sputtering. The interfacial chemistry of the high-k gate dielectric Y 2 O 3 has been investigated on nitrided and un-nitrided Si using X-ray photoelectron spectroscopy. We found that the Y 2 O 3 gate film having NH 3 -based interface layer is very effective in reducing equivalent oxide thickness and leakage current as well as improving film qualities. This NH 3 -nitrided layer is suggested to minimize interfacial YSi x O y formation by limiting the amount of Si available to interact with the Y 2 O 3 layer. These Y 2 O 3 gate dielectrics exhibit excellent frequency dependence and weak temperature dependence of leakage current. They also show negligible charge trapping at high electric field stress.