Hsin-Tien Chiu

Comparison of the diffusion barrier properties of chemical‐vapor‐deposited TaN and sputtered TaN between Cu and Si

This work investigated the barrier properties of metalorganic chemical‐vapor‐deposited (CVD) tantalum nitride (TaN) and physical‐vapor‐deposited (PVD) TaN between Cu and Si. The CVD TaN film had a preferred orientation (200) with a grain size of around 60 nm, while the PVD TaN had a (111) preferred orientation with a grain size of around 20 nm, as determined by transmission electron microscopy (TEM) and x‐ray diffraction (XRD) analyses. Degradation study of the Cu/TaN/Si contact system was also performed by sheet resistance measurement, scanning electron microscopy (SEM), XRD, secondary ion mass spectroscopy (SIMS), and shallow junction diodes. These results indicated that the PVD TaN film can act as a better diffusion barrier than the CVD TaN film. The higher thermal stability of PVD TaN than CVD TaN can be accounted by their difference in microstructures. The failure mechanisms of both CVD TaN and PVD TaN films as diffusion barriers between Cu and Si were also discussed.

Potassium ion recognition by 15-crown-5 functionalized CdSe/ZnS quantum dots in H2O

Based on 15-crown-5 functionalized CdSe/ZnS quantum dots (QDs), we report a novel fluorogenic sensor to probe K+ ions in H2O; recognition of K+ can be achieved via the Förster type of energy transfer between two different color QDs, so that [K+] of the order of 10(-6) M can be promptly detected.

(110)-exposed gold nanocoral electrode as low onset potential selective glucose sensor.

A straightforward electrochemical deposition process was developed to grow gold nanostructures, including nanocoral, nanothorn, branched belt, and nanoparticle, on carbon electrodes by reducing HAuCl4 under constant potentials in mixtures containing CTAC and/or NaNO3. Among the nanostructures, the quasi-one-dimensional nanocoral electrode showed the highest surface area. Because of this, it provided excellent electrochemical performances in cyclic voltammetric (CV) studies for kinetic-controlled enzyme-free glucose oxidation reactions. In amperometric studies carried out at 0.200 V in PBS (pH 7.40, 0.100 M), the nanocoral electrode showed the highest anodic current response. It also offered the greatest sensitivity, 22.6 μAmM(-1)cm(-2), an extended linear range, 5.00×10(-2) mM to 3.00×10(1) mM, and a low detection limit, 1.00×10(1) μm among the electrodes investigated in this study. In addition, the glucose oxidation by the nanocoral electrode started at -0.280 V, more negative than the one of using a commercial Au electrode as the working electrode. This is attributed to the presence of exposed Au (110) surfaces on the electrode. The feature was applied to oxidize glucose selectively in the presence of ascorbic acid (AA) and uric acid (UA), common interferences found in physiological analytes. With an applied voltage at -0.100 V, the AA oxidation (started at -0.080 V) can be avoided while the glucose oxidation still provides a significant response.

Metalorganic chemical vapor deposition of tantalum nitride by tertbutylimidotris(diethylamido)tantalum for advanced metallization

We deposited tantalum nitride (TaN) films by low‐pressure metalorganic chemical vapor deposition (LP‐MOCVD) using a new precursor tertbutylimidotris(diethylamido)tantalum (TBTDET). Strong Ta–N double bond in the precursor preserved the ‘‘TaN’’ portion during the pyrolysis process. This method has yielded low‐resistivity films. It changed from 10 mΩ cm (deposited at 500 °C) to 920 μΩ cm (obtained at 650 °C). The carbon and oxygen concentrations were low in the films deposited at 600 °C, as determined by x‐ray photoelectron spectroscopy. Transmission electron microscopy and x‐ray diffraction analysis indicated that the as‐deposited films exhibited polycrystalline structures with the lattice constants close to the bulk TaN value. The TaN barrier layer was successfully applied as a glue layer for CVD tungsten (W) metallization schemes.

Preparing titanium oxide with various morphologies

Titanium oxide powder was prepared by hydrolyzing titanium tetraisopropoxide (TTIP) in aqueous solutions at pH 2, using TMC and NP-204 as surfactants. The anatase phase was formed when the precipitants were dried at 373 K. When the calcination temperature was below 773 K, all the powders were crystalline in the anatase phase. The powders changed to the rutile phase when the calcination temperature exceeded 1173 K. The powder calcined at 673 K has spherical primary particles with diameters of approximately 8 nm. When the powders calcined at 673 K were heated in NaOH solutions of various concentrations at 423 K for 20 h, titanium oxide powders with different morphologies were obtained. After the powders were refluxed in 5 M NaOH solutions, flower-like titanium oxide particles were formed. Nanotubes of titanium oxide about 8 nm in diameter and over 600 nm long were obtained when the powders were refluxed in 10 M NaOH solution.

Gold Nanostructures on Flexible Substrates as Electrochemical Dopamine Sensors

In this study, we fabricated Au nanowires (NWs), nanoslices (NSs), and nanocorals (NCs) on flexible polyethylene terephthalate (PET) substrates via direct current electrochemical depositions. Without any surface modification, the Au nanostructures were used as the electrodes for dopamine (DA) sensing. Among them, the Au NW electrode performed exceptionally well. The determined linear range for DA detection was 0.2-600 μM (N = 3) and the sensitivity was 178 nA/μM cm(2), while the detection limit was 26 nM (S/N = 3). After 10 repeated measurements, 95% of the original anodic current values were maintained for the nanostructured electrodes. Sequential additions of citric acid (CA, 1 mM), uric acid (UA, saturated), and ascorbic acid (AA, 1 μM) did not interfere the amperometric response from the addition of DA (0.1 μM).

Metalorganic chemical vapor deposition of tungsten nitride for advanced metallization

In this study, the physical and electrical properties of tungsten nitride thin films deposited by thermal decomposition of bis(tertbutylimido)bis(tertbutylamido)tungsten have been investigated. The films have an excellent step coverage over high aspect‐ratio contact holes as well as a low carbon concentration. Strong W–N double bonds in the precursor preserved the nitrogen atoms during the pyrolysis process. This method subsequently yielded low‐resistivity films. A decrease in film resistivity from 4300 to 620 μΩ cm corresponded to an increase in the deposition temperature from 500 to 650 °C. X‐ray diffraction (XRD) and wavelength dispersive spectroscopy (WDS) results indicated that the as‐deposited films have face centered cubic (fcc) phase polycrystalline structures with excessive nitrogen atoms.

Metal-organic chemical vapor deposition of tantalum nitride barrier layers for ULSI applications

Abstract Low-resistivity tantalum nitride (TaN) films were deposited by low-pressure metal-organic chemical vapor deposition (MOCVD) using a new precursor tertbutylimidotrisdiethylamidotantalum. The surface morphology and the step coverage of TaN films were characterized by scanning electron microscopy. The film deposited at 450 °C had nearly 100% step coverage and the step coverage decreased to 25% for the films deposited at 650 °C. The carbon and oxygen concentrations are about 10 at.% in the CVD TaN films, as determined by Auger electron spectroscopy. From Rutherford backscattering spectroscopy and secondary ion mass spectroscopy analysis, TaN films were found to be effective diffusion barriers between aluminum and silicon up to 550 °C. The electrical measurements of diode-leakage current indicate that the Al/TaN Si structure remained stable up to 500 °C, after which Al started to diffuse through the TaN layer and resulted in a higher leakage current.

Syntheses and characterization of organoimido complexes of tantalum; potential single-source precursors to tantalum nitride

Abstract New single-source precursor to tantalum nitride thin films, (But N)Ta(NEt2)3, and relate complexes, (RN)Ta(NEt2)3 (R = Pri and Prn), were prepared by reacting corresponding (RN)TaCl3py2 complexes (R = But, Pri and Prn) with LiNEt2 in hydrocarbon solvents. The structure of (ButN)TaCl3py2 was determined by X-ray crystallography.

One-step vapor–solid reaction growth of Sn@C core–shell nanowires as an anode material for Li-ion batteries

Sn@C core–shell nanowires (NWs) were synthesized by reacting SnO2 particles with a flowing mixture of C2H2 and Ar gases at elevated temperatures. The overall diameter of the core–shell nanostructure was 100–350 nm. The C shell thickness was 30–70 nm. The NW length was several micrometers. Inside the shell, a void space was found. The reaction is proposed to be via a vapor–solid reaction growth (VSRG) pathway. The NWs were investigated as a potential anode material for Li-ion batteries (LIBs). The half-cell constructed from the as-fabricated electrode and a Li foil exhibited a reversible capacity of 525 mA h g−1 after one hundred cycles at a current density of 100 mA g−1. At a current density as high as 1000 mA g−1, the battery still maintained a capacity of 486 mA h g−1. The excellent performance is attributed to the unique 1D core–shell morphology. The core–shell structure and the void space inside the shell can accommodate large volume changes caused by the formation and decomposition of LixSn alloys in the charge–discharge steps.